Snapping Ti bolts 3T ARX team

don't know about a source of quality SS bolts in london, but a screw extractor will retrieve your snapped bolt:

drill pilot hole and insert, the action of insertion unthreads the bolt

and then once you've broken the screw extractor, you find that the only thing hard enough to grind out the extractor is a small stone in the dremel.....

seriously, tho' the screw may be fairly loose and easy to move now that the tension is off it. I'm just preparing you for the worst. Good luck.