Front derailleur won't stay in big ring - it just springs back

you can get a new d-wing by buying cheap shifters, or buy a new shifter set. Simplex retrofriction are great and will probably sort out the initial front mech problem too. Sachs, Suntour, Shimano 105. all are cheap. You probably need a new set anyway.

Well, yeah... but it'll probably be a right job getting the rest of bolt out of the... whatever you call it, the inside of the thing that sticks out of the downtube.