I assume listening to liveatc.net is not the same?
You want to listen to traffic at your local field, to get used to the local procedures and even voices and personalities.
If I pay for each lesson at a time, plus the extras it will be closer to £8,500
So, in effect the school want to borrow thousands of pounds off you at what works out to be a seriously high rate of interest. Why would they want to do that?
There is only one explanation: they need the cash, they have already tried to borrow it from their bank at a sensible rate of interest, and their bank has refused to lend them the money, having decided that they are too high a risk.
If a bank has already decided that they aren't going to risk lending money to these people, you'd be utterly mad to do the same thing yourself.