As far as basing goes Manchester is the significant base and they often run heavy so they can use crews there for the numerous 'W' patterns we cover during the summer. If it says Northwest I would bank on that, secondly Glasgow (usually undersubscribed) and then Newcastle very close behind. However, a third party is covering flights from NCL next summer. Gatwick is rumoured to be getting the 2 additions to the Boeing fleet, but there are a lot of summer contractors just offered permenant destined for any Southern bases. With BHX, BRS being small bases they are very difficult to get and there is no shortage of takers.
Rostering is pretty stable....... However a very busy program (most jets doing slot 3's) and ageing Boeing jets caused an awful lot of disruption to 757/767 Pilots rosters throughout last summer. I found from June-late October I had 3 days off together at best and usually 2 quality days. Lots and lots..... and lots of night Turkeys would also make commuting quite a drag. I would guess you may get a few days away from base, but you know you are workng during the summer!! It is what you make of it.
TCX is a great place to work, very nice people, very good T's and C's and some security.
Good luck.