I don't think there was a discount code but if you call/email them they will do their best on price, which has been quite competitive in the past, even against some of the cheaper online places. Not sure if it helps mentioning the forum or not.
I can see a lot of traffic and mensions from the Z4-forum, just to let you know we have dropped our prices recently in a massive way.
Take a look https://www.tyremen.co.uk/ Any questions please ask.
I had 2 Goodyear Eagle f1 Assymmetric 2 with rim protection fitted at a local tyre place.Price for 2 x 255 x 35 x 18 inch was £260 fitted.This was the cheapest price I could find.