Have never flown from Dunstable, but I did learn to fly at Wormingford. They have a pretty decent trainig fleet, two K13's, a K21 and a grob twin III ACRO. They also have 4 single seaters and I believe 2 winches, so they are have plenty of equipment, so you should always be able to fly.
They fly on saturday, sunday, wednesday and friday.
Which club you choose will depend on what days you can fly and how much you want to spend, most clubs like Wormingford would expect you to do your share of jobs. Typically you would either arrive early in the morning to help get the kit out or stay to help pack everything away. I would arrive early so you can get your name near the top of the flying list.
I would recommend visiting a few different clubs to see which is the best fit for your needs, i flew from several, when I have been visiting different parts of the country and some have a very different "feel" about them
You might also try Cambridge gliding club at Gransden, just up the M11. The best club for you isn't always the closest.
Whichever club you choose I hope you enjoy it