Frodo - great advice about the bike setup. One of the great things about living here in Belgium is that the whole country is bike nutty. There's plenty of guys doing that sort of work for pro-teams and committed amateurs, so they might even let me in. I know the geometry has to be spot on to safely do lots of distance. Thx.
FatBuddah - got it with the slow building. Not making any assumptions that running muscles will makle me capable of cycling. At the moment I can barely walk so I reckon there will be a heap of atrophication going on in the next month, so will have to be very careful in my rehab. Big mistake to get to eager. BTW, the doc didn't say "never again". He's a sub-3h marathoner too and he appreciates the significance of my issue. He said i could possibly do another mara next year if i was pain free. The issue for me is that if I can't understand what has caused such wear and tear, there's no way I want to risk crippling myself. So if I acn turn down running intensity by combining with other sports, that could be a great solution. Am still v. concerned though. I can hardly walk right now and I keep falling over. I hate this feeling of weakness and vulnerability.
bbplodder - funny about ogling over the gadgets and stuff. I've been tough on myself for a few years to resist the attractiveness of it all but given the prospect of losing my running, I think I'll change quickly. The new bathroom might have to wait a (little!) bit.

Penni - it's really encouraging that after some difficulties you can still do an event as tough as MDS. I've always been spot on with running shoes and keeping them well looked after, mileage logged. No need for orthotics, I'm quite light on my feet and fairly neutral in balance. Do you have any ongoing concerns about wear and tear? I never worried about it before. Mr.Wolf's titanium enhancement stories send a cold shiver down my spine.
Cake - cheers mate. Much appreciated. I don't want to be over dramatic but running is something that people would say defines me and how people relate to me, so to suddenly face the prospect of losing it is tough. Good to know other people can relate to it.
Blisters - nice to see you here too. Glad you are keeping up your athleticism and I'll bear the high cadence thing in mind.
Any other tips/ advice/ insights more than welcome. I've got loads to learn. Thanks everyone. 