Hi mandy, they were being a little naughty when they did your cambelt under warranty, because as has been said to change the pump while doing the belts is part only cost (usually) unfortunatley to change it now will be similar labour charge to doing a cambelt, not sure of cambelt part charges, but you will be looking at probably almost £300!! assuming that cambelt parts ~ water pump cost, water pump is usually a preventative change, there is not a service interval on the pump so I would leave alone, won't drop £300 just to get it changed!.
As regards plugs, H4rdy, where do i sent my CV
as it only took me about 10 mins - seriously, the cover is off anyway as I have a CAI, and using cable ties, pulled off the coil packs and then a couple of mins per plug with a plug spanner, push packs back on, jobs a good un
So unfortunatley I don't think you will save any worthwhile money on labour, only on the cost of the plugs.
As regards the belt service interval, different editions of the service manual have different interval's, the general accepted better safe than sorry wisdom is 60k miles, me being ultra safe changed mine at 55k miles!!