Looking at the pictures the caliper and discs are different so I dont think the VWR or Forge are related. Also no idea of caliper clearance for different wheels.
I spoke to Forge some time ago and couldn't find out whether they will fit under 8x18 TD's. After talking to a few who had bought cheaper, seemingly very similar big brake kits I decided not to take the risk. Seems the E46 M3 has a number of kits that seem similar to the AP's most are cheaper for a reason.
DS2500 pads are also more expensive and higher quality than EBC by all accounts.
I'm still sticking with VWR brakes for my upgrade, just wish they were not so expensive.