The official line is that the plugs need doing every 80k on the 3.2, so they should have been banking on doing them at this service. It is frankly a bit ridiculous not to include a standard service item such as this if it's supposed to be a service to manufacturer's recommendations. I don't know where they got 100k from either. 80k+40k = 120k. :-/
It's not a 100 quid job, though, IMHO. Not too bad to DIY if you want to do them.
Automatic transmission fluid change is not on the schedule - only for "extreme conditions" but it's advisable to do it at around this mileage, I'd say. If it's changed before problems start to occur the box will last a lot better.
It's well worth doing servicing yourself, if possible, IMHO. 30 quid gets you enough oil for more than 3 changes on trade club and the fiters are only a few quid each.
Cam belt and tensioner kit is due every 40k / 4 years so they should have done that given they're not expecting to see it for another 20k (don't run the oil & filter for this long - change it every 4-5k). Coolant change is also advisable every 5 years but it's not on the service schedule.
So, a couple of important things missed there. Whatever you do get the cam belt change done at or before 80k - assuming it was done at 40k? (if not, do it ASAP)
Kevin