787 is a lovely machine. It's not without it's gotchas but I trust your experience of thinking "how will it kill me now?" with the Q400 should serve you well on the 78. I imagine turbo prop to heavy jet will probably be quite the learning curve but I've never flown a turboprop so wouldn't know.
LH rosters can be busy, especially winter time, but in the summer 14-15 days off per month and some short haul flights can be expected. I don't believe there are any short haul flights from BHX though...maybe they'll send you to MAN/LGW for a few over the summer but I have no idea.