Having transferred from T3
's train station i'd say you have plenty of time. Its a bit of a long walk (10-15mins with baggage), via T1 and then along the skylink moving walkway but you should be fine aslong as your flight isn't delayed by too much.
edit: dunno why I thought you were on BA into MAN (just got out of an exam, mind must be tired), in anycase FR use T2 and that is a shorter walk to The Station. FR are usually punctual - except of course for the only time i flew them into MAN.
[Edited 2004-05-21 12:46:24]