Why wait until Christmas?
Just got to the gliding club next Saturday or Sunday. Unless the weather is horrible, there probably will be activity there. In fact, most clubs will have some sort of mechanism (either call a number or visit a website) that will tell you whether they're going to be launching that day.
Show up, tell them you're enrolled in a course starting Christmas and that you want to sample the atmosphere. You'll probably be able to hang around all day, talk to the people there, watch the launching and landing in action (so you know what kind of gloves you need, if nothing else) and if you're lucky you'll be squeezed into the schedule for a trial flight anyway.
If you talk to the right person you can probably pick up your joining pack right there and then too. Gives you something to read over the next few weeks.