If spending £35 on a 1MB expansion (with Real-Time Clock and A1200-style clockport) is too much, how about one of those 8MB Fast RAM expansions Zetr0 is building and selling for £30 over on EAB?
Personally, I think they're both very well priced considering the current situation, even if I can't afford them right away. Compared to years ago, these are pretty bargain priced.