Should I ride my first fixie back from the shop (in London)?

London not even dangerous, fucking hell, one of the biggest myth about London.

I'll bet my experience of cycling in London against your's Ed. That's a shockingly complacent thing to say. It may not be as dangerous as non cyclists think, or cyclists from outside London think, but there are still considerable risks. There are new threads started almost every day about accidents, near misses or examples of how members only escaped because they have experience of riding in traffic.