Had my right knee done about 15 years ago after I tore it running (mugs sport tbh lol), had a week off work and about 6 or 7 weeks off the bike but have had no problems at all since (with that knee). I would advise flat pedals when you get back to cycling at least for the first few months
Welcome Captain, if you whisper me your address I`ll drop you a copy of Riders Digest which has adverts for most of the London Courier Cos in the back, its a crap Motorcycle courier mag, but the adverts are there
As far as blocking the exhaust and blowing the engines (head?) gasket a large potato is much better, screw it onto the pipe nice and tight and watch from a distance. Lovely. Bit more visible than a banana tho
Another vote for virgin, never had a problem with them at all (crossing fingers now)