I don’t have a full computer going spare, but I do have a 256gb m.2 SSD I’m happy to donate - may be useful if someone else has a pc without a hard drive
Assuming you want a desktop. Micro PCs from Dell and HP can be had on eBay for £130-£200 with 16GB RAM, 120GB SSD, and a CPU in this ball park, although you’d need to probably look up the exact model for support.
I am pretty sure I have some spare pc parts. I can’t remember exactly but I have a CPU, cpu fan, and some ram (maybe 8gb) lying about. I can check the exact specs this evening or tomorrow if that’s helpful
I have a fairly ancient i7 gaming PC still kicking about at my parents up in Peterborough, but I’d probably rather chip in for a new one over carting it down on the train!