Some of what Gertrude the Wombat says is true, but overall I don't think it quite hits the mark. You will do a fair amount of short flights while training, but that is not the whole story. Not every landing ends up being a forced landing, often my landings are because I'm tired or need to use the little boys room.
Soaring can be cheap. Last Saturday for a $17 USD tow I flew my L33 around for 2.3 hours. That's cheap. Of course add in my hull insurance costs, monthly club dues, it is not quite as cheap as the $7.40/hour. But still not bad.
Soaring is very weather dependent. You can fly in all sorts of weather, but you need the good soaring weather to have those kind of flights. Maybe GTW has only experienced gliders in the wrong kind of weather. Maybe that's the norm in the UK. I don't know.
If flying was the language of man, soaring would be its poetry.
Some folks do big x-c flights in gliders. 50, 100, 1000km. Cross country is a challenge in a glider, not like pointing your propeller in some direction and droning away. If you fly for the challenge this is good.
I think RatherBeFlying has good advice, I would concentrate on power first, or at least pick one to concentrate on and stick with it. Some diehard glider guys think gliders first is the way to go, as Arclite01 says. And, if you are to end up like them, there is some advantage to starting in gliders. But I don't think it is a huge penalty in learning in power first, then going to gliders. Makes an easy transition to gliders, in the US it is a very easy transition to a glider rating. Takes longer to learn the art of soaring, in some respects a lifetime.
-- IFMU