If your clutch judder is slight it might just be normal, I wouldn't have thought you'd need to replace your clutch?
You will need a cambelt on the 60k/6yr service but I've heard of Lexus dealers doing it as cheap as £180.
The new IS250 is nice, I think the road tax is in fact cheaper than the IS200 because the emissions are below 225g/km, putting it into the lower tax band. But I don't know if I'd buy a new one in the current climate, could lose a lot of money. Personally, I'd keep what you've got until things settle down a bit.