Hiya,
As Bog says, we have just moved into an industrial unit - It has taken many many years and luck to get what we needed (not exactly what we wanted, but just about big enough!)
We started looking for new premises in about 2004. We approached the council who told us that we would not get 'change of use' on a building on an industrial estate, and told us to look into educational buildings instead (We never did this as we were already in a school and it just wasn't working for us!) So we persevered...
Skip to 2009. After many many viewings we looked at an industrial unit which was right next door to a judo club.
We had many conversations with the local council again. They argued that the judo club had been there for many years, before the new legislation had come in that sports clubs could not be housed on an industrial estate, so we still didn't really stand a chance. (We didn't really accept this!) We set up a meeting with 2 people on the council who we managed to convince it was a good idea to allow us to move in! They informed us that since the government had changed, there had been a change in thinking - there were far too many industrial units standing empty so all uses would now be considered! We were also in luck, for the fact that the 'blast zone' for a chemical company up the road had recently been reduced and the unit we wanted was no longer included in it! We decided to spend the money and apply for change of use. We had to do our homework - we stated that the estate was in a deprived area and we were keen to get the local school children in to use the gym either for free or at a reduced rate. We worked out exactly how many cars could be parked outside the building etc etc.
From then on, things moved pretty quickly. We kept in touch with the sport development team and the councillors we had the original meeting with. One of them was actually on the committee which decided whether we would get change of use so he couldn't really tell us anything, except 'it's looking good'!
In August 2010 our application was accepted and we got the keys on 16th September!
I'd say keep persevering, get in touch with absolutely anyone who can help and keep in touch with them. Find other sports club's on estates in you area, or even fitness gyms and if possible find out how they managed to get there! Get in touch with someone on the planning committee on your council. Find out what the council want to do such as regenerating deprived areas etc. Do anything you can to get what you want!!! It's hard work, but so worth it in the end.
It's happening more and more these days so don't give up and don't take no for an answer!