You can commute from pretty much anywhere in the UK on the 'bus but you'll still need a room for a few nights each month between tours. I believe junior blind lines on the 'bus consist of lots of early, 3 and 4 day tours over weekends. Expect to check in around 05:30-06:30 for those, so you might need a room if you can't get to LHR in time in the morning. You'll probably get some day trips as well so you may need a place to stay between those too.
I don't think there'll be many places on the 757/767 fleet for new joiners as that now the second most popular fleet in the company and half of the Airbus FOs seem to be bidding for it. Mind you they said that about the 744 too so anythings possible.