Just personal preference for me, but I always take the head off. Makes moving the individual pieces easier; just my preference. The connectors aren't bad to disconnect and reconnect after you've done it a hundred times
Make sure you have "Standard" measure sockets, not "Metric" since you're in the UK.
No WD-40 near a pinball machine. I've never once found a situation where WD-40 makes things better. It just doesn't.
Have fun! Good luck! If things don't work when you bring it home and set it back up, re-seat the connectors. Usually one or two have loosened up during the trip.