7miles,
I know people being pulled out of the hold pool almost immediately, as recent as 2 weeks ago, ie get the call to say you have passed the sim, job offer at same time. Don't think the pool is very deep at the moment!
As for aircraft type, if you have >2000hrs, you will very likely get the -400, as far as I know no-one been offered the 777 yet but the plan is for ~50 DEPs for the 777 this year: courses will probably start to materialise later as the 4 new hulls start to arrive. Less than that, you will get A320 LHR. LGW A320 usually the destination for SSPs/cadets.
There is a small trickle of 757 courses, nearly always going to type rated guys.