My ticket is purchased and I've finally received my entry clearance. Everything is working out well. Both my work permit and entry clearance are valid for longer than my passport (which expires in three years). Hopefully there won't be too much paperwork to get my entry clearance transferred to my new passport, but I have plenty of time before I have to worry about that.
I've had to start telling some friends that I can no longer fit them into my schedule as I'm booked solid until I fly out. Fortunately, I've had plenty of time to see most of them before I leave, so it's not too bad, but I'm going to be a tired puppy on the flight as I'll be a non-stop whirlwind for the next couple of weeks.
Looking forward to seeing some of my friends in the UK!