You'll find that the more posts there are in a section the more people will join up with those cars. (So the MG forum will fill up more quickly now.)
The cams are fitted in pairs, overlap is the only thing you want to avoid. If the exhaust opens fractionally at the same time as the intake you can get all sorts of nasty things happening. If you buy a pair then this is taken into account.
Always change the cam belt & tensioner. Check the valve springs as well whilst the head is open.
Which cams are you going for then?