I went to buy an altimeter, popped into the office, had docs checked and introduced to the chief instructor, who showed me round and then found myself on a load - 'cos there was a slot'
I was about to leave when the tannoy said there was a slot on the next lift and although the rig I had hired was not packed, they let me use its identical twin - I had to go then due to family, but went back for more of the same the next day..
If you are near Kent give it a go, you may be pleasantly surprised.