I still own and use my original X250, which I bought new in 2015. I recently replaced the batteries and swapped out the internal Wi-Fi adapter for a €20 AX210NGW. It's almost laughable how easy both upgrades were. Everything works out of the box with every Linux distro I've tried, including the fingerprint sensor.
I prefer the keyboard on my T430, but the much better screen, slimmer form factor, and still pretty good keyboard make the X250 one of the best devices I've ever owned.
Dual batteries: my X250 on Linux, I'd like to set it up so when the external battery gets to 20% or less, the internal battery starts draining and the external no longer discharges. Can't work out how to do it. Tried Gnome/KDE and Debian/Fedora. Anyone cracked this?
PS: Mine was £100 as well, seems to be the going rate here in UK or was.