Well if you don't much like FastFrames - which I must admit have served me pretty well- then try Great Art wwwGreatart.co.uk who sell Nielsen and other frames, the former appearing to be sourced from Nielsen's German operation rather than the UK.
Actually Nielsens distribution policy in the UK does appear hard to understand. They appear to want to work through retail and framer distributors rather than supply small quantities direct to end users, which I can understand;but I've also had Fastframe orders delivered by Nielsen themselves. They supply me direct on mounting materials, and then you get the utter joy of trying to work out which of the UK codes relates to what product numbers from Germany if you place a frames order on Great Art.
Still, keeps the mind active I guess!