Put my dummy back in...
Thanks for the thoughts folks. Basically what happened was thusly. Running slightly late for work, saw lights ahead green and thought 'I can make that', out the saddle and hard on the pedals, at which moment the chain skipped off the chainring. I was down before I knew it.
Out for somewhere between 5 and 10 seconds, came to with a couple of guys (one cyclist, one pedestrian) trying to help me. Dazed, legs not quite working, but I got out, felt the blood on my head, staggered round the corner to work where, despite my protestations, a colleague decided that no, I wasn't fine, and the bleeding wasn't likely to stop soon, and took me to Minor Injuries. Where I realised I'd got quite a thump when I couldn't remember my address or the name of the colleague who had driven me there. They sent me on to A&E (same colleague took me), by which time I was compus mentis, and got a staple put in the wound.
Video camera got broken off off the bike, but it fine; cycling troos and jersey a bit scuffed but serviceable; metal edge to Brooks grips worn quite dramatically; both wheels knocked slightly out of true, but re-trued nae bother yesterday.
Perhaps got lucky, given I hit the ground hard. Worst thinkg is, as trauma can do, my pericarditis got triggered. At least I think it's that and not bruised ribs. Got back on the bike properly yesterday, wee 17 mile jaunt into East Lothian, speed limited more by the inflammation around the ribs that anything else as heavy breathing gets painful, then commuted today. Good to be back on, the bus last week was a sauna-like nightmare.