They are becoming quite sought after especially if you want the original 84/85 model before they started putting on the brake cable guides on the frame etc. You are best trying the US as they do not often come up for sale over here
You are doing well if you find one for under a £100 especially in the UK.
Biagio did have a couple of old full bikes he was trying to sell a few months back
My 85 I got from the States early this year cost £100 + shipping and although it was straight with no dings etc it needed a full strip and re-powder.