You may want to look into this repo https://github.com/hamishcoleman/thinkpad-ec
and create a bootable image with your preferred BIOS update (without switching to x220 layout). This will trigger an EC firmware update for the keyboard. I'm not sure about alternative layouts, it might take some modification if UK is not natively supported, but that should be easy enough to look up. In that vein, it also might be worth checking out what key press events are being logged to see where the issue lies. On Windows, run eventvwr.msc, on OSX, check out Karabiner Elements for a sanity check that it's not an OS layer issue.
ThinkPad X230, i7-3520m, 16GB RAM, 1Tb Crucial MX300, 1Tb Samsung 850 msata, Intel HD4000, 12.5" FHD