Quite how much you pay is your affair, but £150-ish for this lot doesn't seem unreasonable. However if you let a polystyrene hull get within ten feet of polyester resin it will dissolve. Don't go there!
BTW I'm pretty sure that there's a review of this kit by Terry Small in the pipeline at MB magazine, due any time now. I've certainly been asked for wiring diagrams (see ACTion website, under 'Theodor Heuss').
FLJ