Hi.
I'm pretty new to this site and have been reading what all you girls write and find it quite interesting.
Sarah - I know the gym you are talking about as I used to work there as a Fitness Instructor when it first opened.
It is a large, busy gym, however, it does have it's fair amount of trouble there. If you consider that you may be leaving in the evening you might want to look around the car park and the people hanging around. Sorry to be the bearer of bad news, but personally I think you should definately look at your other options.
Croydon is a very busy town centre, however, I think what the other lady said about 'up market clientele' could be correct - no offence, but a large percentage of people will just be happy to pay to go the the 'chop shop' for their nails.
I would consider the areas, just outside, i.e., Purley, Sanderstead, South Croydon - even West Wickham. These are the areas have are a little bit more 'affluent', have good transport links and ladies who have a little bit more time on their hands to have beauty treatments.
I hope that this helps - if you want any more info let me know.
I hope I haven't offended anyone, but having lived and worked in Croydon I think I'm quite well informed to give this sort of advice.
Good luck!