I know you said UK preferably, but try RH Factor Guitars in the USA. Bought Tone Riders from them twice in the past before there was a local distributor and fairly recently got some guitar hardware as well. All around good experiences with them - and they have stock of Rebel 90s at the moment. Shipping should be around $25 for USPS Priority based on past experience.
http://rhfactorguitars.highwire.com/product/tonerider-rebel-90-set-r90-nickel-covers