Is there no mechanism for reporting or complaining about flying schools to the CAA? We see stuff like this time and time again on here.
If you have paid up front for them to deliver training, and they subsequently do not deliver that training, then if anybody has broken a contract it is them and they should refund.
Perhaps it would be a good idea to keep a diary. If you turn up to go flying and the lesson is cancelled, don't just take it, ask them why and write it in the diary? If they are palming you off with excuses of things like high wind, check the wind yourself, see if other light aircraft from other schools are off flying, again write down your findings in the diary. If they're as bad as you say, a pattern will soon build up, and you will have something to hit them with and show to the CAA or whoever to back you up.
I really hope it turns out ok for you,
Unstable_aloft