Thanks Stef.
I don't think the LM317T is cheaper than the 7818
per se. In fact the equivalent Velleman PCB with a LM317T on it from CPC is more costly at £8.75 including VAT:
http://cpc.farnell.com/velleman-kit/...18?Ntt=HK00218
But it's a fair point; keeping some variable voltage regs in stock is always a good idea.
N.