CEX supplied a 300gb IDE drive, a Mac USB keyboard, and a Mac Pro mouse for £21 + £2.50 P&P. The keyboard and mouse are black, which isn't ideal, but they work properly and have the all-important eject key etc. So now I'm just waiting on the memory to arrive before opening the main casing and swapping out the drives etc. Looking out for cheap Apple speakers but I'm not holding my breath, I was ridiculously lucky last time. Hopefully I'll get it done for under £100 and sell it for over £200; that's not a huge profit considering how much time and work will go into it, but I can live with that.
The other thing I'm hoping to find is some software; I bundled a copy of Office 2004 and some games with the last one but my last spare copy of Office already has several bids on eBay so I don't want to pull it from sale. If anyone spots any software suitable for a G4 processor and OS-X Leopard in e.g. a charity shop please let me know. It isn't crucial because I can install Libre Office and some other freeware, but it would be nice.