Hi and thanks for all the replies.... a lot to take in....penetrating slowly.
The shift register route seems like quite a good one if I could get it to work. The relays I plan on using are made by Finder and have a 12v coil and draw about 45mA so if a TPIC6B595 can switch this then it'll save me making up transistor buffer. Any rate, I've ordered a 74HC595N from CPC in the UK http://goo.gl/pejJ91 so that I can experiment....probably something I should know about.
However the idea of all those pins on a Mega is very appealing, but are there good and reliable copies made which I can get in the UK? Or should I think about buying from abroad?
Many thanks
Ron