Trade: Wanna swap your bike for a blad?

well, depending on your deffination of stiff, maybe go with oversized alu tubes for maximum stiffness, mind you will comprimise ride quality, £550 will get you plenty of bike! size-wise im retarded so il wait for someone else to comment on that, might be worth telling us your inside leg legnth. . . imo go for 531 frame or 653 if you can get it on the cheap, get a old road double for crankset and get help with chainline and then £150 on wheels (including build, on one hubs to open sport are a good choice) and voila. . .

I don't think you've particularly understood the man wants a ready-to-ride swap here.