In reply to Onion: Just thought I'd feed back as I went ahead and bought the ETTL version of the ones I mentioned above. As someone else mentioned, TTL isn't always / usually a necessity, but for me it was worth having because I mainly shoot weddings with controlled lighting and then moving subjects, so very different obviously if you're shooting controlled climbing shots etc.
Anyway, I got two units for £60. Best range with direct line of sight that I've had with them this evening was about 150ft give or take, but I ran out of space a bit after that. I've tried them at closer range through brick walls and they were firing fine from one side of my house to the other, so through three sets of bricks and 30ft distance.
That's about it for now - just a quick play around but on first impressions they do the job. I prefer these to the (same brand) non-TTL ones I had before. Bigger than I expected though - about the size of a credit card and 2cm deep, so not the most discreet of bolt-ons, but not too heavy.
All in all, a thumbs up from me. Wish they were a bit smaller and sexier but in terms of functionality they seem to push the right buttons. Can't complain for the price at all.
BTW, these basically make my previous radio triggers redundant so if anyone wants them give me a shout, lob a few quid into an MR collection pot, and I'll stick them in the post to you.