Hi Gareth,
If you have bought the 378mm kit, then only certain Motorsport rims will fit over these.
Ideally (as you are running Konis), you want either Mo's or TH2s in 8J x 18 ET15
. Any other type of wheel would need trial fitting (inc some 19s). If you buy some second hand Mo's, make sure they are either the old style ones or the very latest new style ones, as the first batch of the new style ones did not have the centres correctly machined for clearance of these size brakes.