Welcome Rachel!
You should check out the radio rallies as they sometimes have computers (I picked up a working Plus/4 for £40 and there was an Amiga 1200 for £120 at the rally near me I went to at Princethorpe
A few examples here:
https://www.nationalhamfest.org.uk/
http://www.g4rga.org.uk/All.html
I love Weymouth and have been a few times as well as getting my RYS sailing one with the sea cadets there in 1993!