I haven't done anything weird I don't think. Haven't changed any of my sources or anything like that.
When trying an apt update I get this:
[~] ∞ sudo apt update
Hit:1 http://ppa.launchpad.net/elementary-os/stable/ubuntu xenial InRelease
Hit:3 http://ppa.launchpad.net/elementary-os/os-patches/ubuntu xenial InRelease
Hit:5 http://ppa.launchpad.net/peek-developers/stable/ubuntu xenial InRelease
Hit:6 http://gb.archive.ubuntu.com/ubuntu xenial-backports InRelease
Hit:7 http://ppa.launchpad.net/team-xbmc/ppa/ubuntu xenial InRelease
Get:2 http://gb.archive.ubuntu.com/ubuntu xenial InRelease [247 kB]
Hit:8 http://security.ubuntu.com/ubuntu xenial-security InRelease
Get:4 http://gb.archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB]
Get:9 http://packages.elementary.io/appcenter xenial InRelease [4,840 B]
Hit:10 https://dl.yarnpkg.com/debian stable InRelease
Ign:11 http://gb.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
Hit:12 http://repository.spotify.com stable InRelease
Ign:13 http://gb.archive.ubuntu.com/ubuntu xenial/main i386 Packages
Ign:14 http://gb.archive.ubuntu.com/ubuntu xenial/main Translation-en
Hit:15 http://gb.archive.ubuntu.com/ubuntu xenial/main amd64 DEP-11 Metadata
Err:15 http://gb.archive.ubuntu.com/ubuntu xenial/main amd64 DEP-11 Metadata
Hash Sum mismatch
Get:16 http://gb.archive.ubuntu.com/ubuntu xenial/main DEP-11 64x64 Icons [409 kB]
Get:17 http://gb.archive.ubuntu.com/ubuntu xenial/restricted amd64 Packages [8,344 B]
Get:18 http://gb.archive.ubuntu.com/ubuntu xenial/restricted i386 Packages [8,684 B]
Get:19 http://gb.archive.ubuntu.com/ubuntu xenial/restricted Translation-en [2,908 B]
Get:20 http://gb.archive.ubuntu.com/ubuntu xenial/restricted amd64 DEP-11 Metadata [186 B]
Get:21 http://packages.elementary.io/appcenter xenial/main amd64 DEP-11 Metadata [6,508 B]
Hit:22 https://deb.nodesource.com/node_8.x xenial InRelease
Hit:23 https://cli-assets.heroku.com/branches/stable/apt ./ InRelease
Get:24 http://gb.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages [7,532 kB]
Get:25 http://gb.archive.ubuntu.com/ubuntu xenial/universe i386 Packages [7,512 kB]
Ign:26 http://gb.archive.ubuntu.com/ubuntu xenial/universe Translation-en
Get:27 http://gb.archive.ubuntu.com/ubuntu xenial/universe amd64 DEP-11 Metadata [3,410 kB]
Get:28 http://gb.archive.ubuntu.com/ubuntu xenial/universe DEP-11 64x64 Icons [7,448 kB]
Get:29 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [558 kB]
Get:30 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main i386 Packages [541 kB]
Get:31 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main Translation-en [226 kB]
Get:32 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main amd64 DEP-11 Metadata [299 kB]
Get:33 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main DEP-11 64x64 Icons [199 kB]
Get:34 http://gb.archive.ubuntu.com/ubuntu xenial-updates/restricted amd64 Packages [7,772 B]
Get:35 http://gb.archive.ubuntu.com/ubuntu xenial-updates/restricted i386 Packages [7,772 B]
Get:36 http://gb.archive.ubuntu.com/ubuntu xenial-updates/restricted Translation-en [2,548 B]
Hit:37 http://gb.archive.ubuntu.com/ubuntu xenial-updates/restricted amd64 DEP-11 Metadata
Get:38 http://gb.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages [486 kB]
Get:39 http://gb.archive.ubuntu.com/ubuntu xenial-updates/universe i386 Packages [470 kB]
Ign:40 http://gb.archive.ubuntu.com/ubuntu xenial-updates/universe Translation-en
Get:41 http://gb.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 DEP-11 Metadata [163 kB]
Get:42 http://gb.archive.ubuntu.com/ubuntu xenial-updates/universe DEP-11 64x64 Icons [208 kB]
Get:43 http://gb.archive.ubuntu.com/ubuntu xenial-updates/multiverse amd64 Packages [8,932 B]
Get:44 http://gb.archive.ubuntu.com/ubuntu xenial-updates/multiverse i386 Packages [7,992 B]
Get:45 http://gb.archive.ubuntu.com/ubuntu xenial-updates/multiverse Translation-en [4,460 B]
Get:46 http://gb.archive.ubuntu.com/ubuntu xenial-updates/multiverse amd64 DEP-11 Metadata [2,516 B]
Get:47 http://gb.archive.ubuntu.com/ubuntu xenial-updates/multiverse DEP-11 64x64 Icons [7,765 B]
Ign:40 http://gb.archive.ubuntu.com/ubuntu xenial-updates/universe Translation-en
Get:40 http://gb.archive.ubuntu.com/ubuntu xenial-updates/universe Translation-en [257 kB]
Err:37 http://gb.archive.ubuntu.com/ubuntu xenial-updates/restricted amd64 DEP-11 Metadata
Hash Sum mismatch
Hit:48 https://packagecloud.io/slacktechnologies/slack/debian jessie InRelease
Fetched 617 kB in 3s (158 kB/s)
** (appstreamcli:7929): WARNING **: No origin found for file ppa.launchpad.net_elementary-os_stable_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz
** (appstreamcli:7929): WARNING **: No origin found for file repository.spotify.com_dists_stable_non-free_dep11_Components-amd64.yml.gz
** (appstreamcli:7929): WARNING **: No origin found for file gb.archive.ubuntu.com_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz
** (appstreamcli:7929): WARNING **: No origin found for file gb.archive.ubuntu.com_ubuntu_dists_xenial-updates_restricted_dep11_Components-amd64.yml.gz
AppStream system cache was updated, but problems were found: Metadata files have errors: /var/lib/app-info/yaml/gb.archive.ubuntu.com_ubuntu_dists_xenial-updates_restricted_dep11_Components-amd64.yml.gz, /var/lib/app-info/yaml/gb.archive.ubuntu.com_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz, /var/lib/app-info/yaml/repository.spotify.com_dists_stable_non-free_dep11_Components-amd64.yml.gz, /var/lib/app-info/yaml/ppa.launchpad.net_elementary-os_stable_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz
Reading package lists... Error!
E: Failed to fetch store:/var/lib/apt/lists/partial/gb.archive.ubuntu.com_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz Hash Sum mismatch
E: Failed to fetch store:/var/lib/apt/lists/partial/gb.archive.ubuntu.com_ubuntu_dists_xenial-updates_restricted_dep11_Components-amd64.yml.gz Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old ones used instead.
E: Problem executing scripts APT::Update::Post-Invoke-Success 'if /usr/bin/test -w /var/cache/app-info -a -e /usr/bin/appstreamcli; then appstreamcli refresh-cache > /dev/null; fi'
E: Sub-process returned an error code
E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/gb.archive.ubuntu.com_ubuntu_dists_xenial_main_binary-amd64_Packages
E: The package lists or status file could not be parsed or opened.
