The range of wheels we supply is on our website www.prodrive.com the only information it doesn't have is the offset of the P-FF7 which is ET51. In the US the wheels are technically the same but the colour range is slightly larger than the UK with an additional colour called British Pewter which is actually really called Grigio Uranio if you want to use the Italian name. This wheel is the same colour as the WR1 wheel although there are some small differences between the two specs.

In the US and Japan we sell various other wheels which are manufactured for us in Japan, primarily for that market. Unfortunately these are not always available in the offsets we require here (most wheels that would fit over the Brembo calipers are ET43 for example) so we do not bring them into the UK. So the reason we don't bring them here is that they don't work, this isn't a conspiracy to deprive the British of anything, other than wheels that won't fit your car properly.

Bright flitter is a colour used on the P-FF7 which is ET51, the ET53 and ET46 wheels are the P1 (P-WRC1). In order to make sure that the offsets couldn't be mixed up, we don't do different offsets in the same colour so the ET53 wheels are gold, silver and anthracite, the ET46 are rally gold and crystal titanium.

Ref offset and fitment to the 'Classic' cars, when we were developing the P1 we always wanted to offer the car on 18" wheels and the original development spec was set at ET50 with an 8x18" wheel. In most conditions this was OK as the development car did not have the rubber lip on the rear arch so only touched in extreme conditions. This wasn't an acceptable solution for release so we changed the spec to a 7.5x18 ET53 which does clear when used with the Pirelli or another similar shaped 225/35 tyre. We did try it with other tyres the same size but found that we had a foul as most other tyres this size had kerbing ribs or similar bulges in the sidewalls. If an 8x18" wheel must be fitted then ET51 will be as good as you will get but don't expect to bolt them straight on and not have to do anything to make sure they don't catch.

Another thing to consider is that the suspension should be given a thorough make-over as well. Fitting 18" wheels sharpens up the whole car quite considerably and if your std suspension is even slightly worn or the geometry is not perfect you will end up with a car that is at best unpleasant to drive and at worst, downright dangerous.
Some time ago I had the misfortune to see what was left of a std car fitted with 18" wheels that had been involved in a very serious accident and the only thing we could put it down to was getting out of phase with the steering over a series of bumps because the driver may have only had one hand on the wheel.

I hope this clears up any lingering issues.

Regards

Mike