Yeah, you probably won't need the spacers. Its better that they touch the inside of the front arch as this won't damage the tyre, unlike if they touch the rear! Although the MOT guy may be interested, thats the only issue.

Regarding that price, a set of 17" wheels with tyres for £400 is certainly not to be sniffed at. If they are from an Alloy Wheel dealer, I would ask for a price with a better tyre. You never know, maybe they will do a proper branded tyre for a little extra money. Worth an ask IMO.