Not sure that microlights are cheaper than gliders once you are cleared cross country.
In a Discus club glider - launch £35.50 soaring cost £37.20/ hr max 2 1/2 hrs chargeable.
So a 2.5 hr flight would cost you £131.50 after that it is free! A typical soaring flight on a summers day can easily be 5+hrs Ok you have to join the club as well.
The expensive bit is the training.
If you would like to visit Lasham and have a look at the setup I would be delighted to show you around. PM me