Honest, this is the last time I'll blether on about this subject for a while. Really. The Nikon D50 is nearly £200 quid cheaper than the D70. And it's got the same lens interchangeability. And here's the clincher: look at these test results: the D50 has significantly less noise at high ISO than it's more expensive relation.
So that's the decision made. Barring some unforeseen financial calamity putting an unavoidable call on the saving-up-for-a-camera fund, I should be able to buy the blighter early in the spring. Until then, I'll try to leave the subject alone.