I've just started to get back to my regular routine at the gym (try to go 3 times a week or so). My attendance got pretty bad from the end of the summer to Christmas, but I am back on track now. When I go I do a mix of cardio (either treadmill or elliptical and rowing), weights, and the 20 minute instructor-led 'tummy session.'
I joined the local leisure centre when I first got here. It's not the nicest gym (and not that cheap either!, but hey, this is London), but it has everything I need, and there is no contract. One thing that is great about it is that personal training is pretty much free. They have a whole program they set you up with when you join, and you meet once a week or so for the first month, and then you can basically schedule further appointments as and when you feel you need a change to the program. No extra charges. I used to take advantage of that when I wasn't working, but don't so much anymore.
I am going to try out one of the other gyms in the council network (you can use any of them with the membership). It will be a bit further away, but was recently refurbished. Also, I am going to start doing Hatha yoga again this week. I haven't taken a class since I moved here, and I REALLY miss it.