Congratulations on your weight loss!
Granted, I'm not clued up about gym prices outside of London, but that seems like a pretty good price. Would it be possible to join on a month to month basis to see how much you would use it? That would be my suggestion.
It sounds like this is important to you, so I think I would go ahead and do it. I'm very into going to the gym as well, and recently took a hiatus for 3 months, as I'm currently living in Brussels where the gyms are crazy expensive, and I wanted to save my money for other things. I will say, that I miss it a lot, and while I can get my workouts through other means (walking, jogging outside) I really do miss my routine at the gym and am feeling the effects.