Thanks for the info Evan and Wayne, and that's the set I was looking at. Yes, I've had quite a bit of experience with vac formed parts, or at least, heat-moulded ones I've made myself, where the finished product is more or less the same thing.
I normally mould my own canopies and some parts from white plastic sheet too. However, the Tempest and Sea Fury canopies in this scale might be a little tricky for me to carve the master for nowadays, due to this bl**dy Arthritis, so I thought, for the price of the set, compared to the cost of clear sheet, balsa, varnish etc, and the inevitable one or two failed attempts, I might as well go against my own principals and buy the dreasded 'aftermarket' parts! I'm going to have to get some resin wheels for the Tempest anyway, as there's nothing much I can do with the kit wheels, and I've already ordered my first resin accessory, in the form of 1/32nd scale 'porcupine' exhausts for the Beaufighter. Have to watch it, or I'll soon be taking the easy way out and using PE parts.......