Yes, I remember AF/KL moving over to T3 from T2 about 6 years ago when AF canned its night stopper and codeshared on BE. Before that of course, the two used to co-exist in T1 prior to them becoming part of the AFKL group.
My point is though is some seem to like to assume that LCC's can just be told where they are being handled at an airport and will simply accept that. Thats not to say that one of those airlines might settle for the older or more basic terminal if it suits its operational needs but in case of FR & EZY at MAN (and LS too) they are the airports biggest customers. They provide the critical mass and the large numbers of passengers which airports ultimately draw money from directly these days. Those airlines are much sought after by airports right across Europe and as such, they can be demanding customers.