Please let us know how the hire experience goes.
Well, results are in - picked one up from a locker under Liverpool Street Station after work tonight. Unfold wasn't too difficult in the end, although I did as
@Dogtrousers suggested and jotted down a cheat sheet to remind me of the order of the process, which did help. First time took me just under a minute, then got it down to just over 30 seconds the second time I had to do it (post-train at the other end of my commute).
The folding back up however was a little more problematic - could not work out where the clip was that was going to hold the front wheel in place and took me a good few minutes to figure it out in the middle of Marylebone Station. A guy nearby saw I was struggling and came over to help and I thought he was probably a Brompton owner who'd "been there, done that" but no - turned out he was merely a sympathetic bystander and also had no clue what to do! I ended up putting it all back together again and starting from scratch and this time it all clicked into place (physically and metaphorically) and got it folded for the train journey slowly but surely. Folding it up again at home, it still took longer than it probably should have done, but at least I knew what I was doing this time. Will improve with practice.
As for the ride itself, I quite enjoyed it. Not as twitchy as I thought it might be with small wheels, but at the same time quite nippy. Gearing was bigger than what I'm used to, but then I was probably comparing it to a Santander Cycle (the only other 3 geared bike I occasionally ride in London); my route to Marylebone and then to home at the other end of the Chiltern line was fairly flat, but even then I was in the middle gear 90% of the time.
Will do some further riding across the long weekend, then return it on Monday or Tuesday (depending on how bad next week's Tube strike is), then give it some thought as to whether I want to buy one or not.