A quick fix for the sticking roof is to pop into halfords and buy a pair of elasticated velcro straps for about £5. Then loop them around the sticking roof bar and the one behind it, either side, stretching them a bit. That way the functioning roof bar pulls the sticking roof bar backwards and you have no need to pull it back manually.
You can also get them from places like focus or b&q but they are about £7 - £8 there.
Hope that helps...
ps: I read somewhere that this method of fix is also the official MG one. See here for pic
http://forums.mg-rover.org/showpost.php?p=1202385