Pielander,
I have had some marvellous times flying at Derby & Lancs (DLGC) in the peak district (near Buxton, not too far from Sheffield, S. Yorks)
www.dlgc.org.uk. They do residential courses, but not as many as they used to. Not a plug, I'm not a member!
I've also flown out of Rufforth (10 years ago) which had a great bunch of people then, but much poorer facilities.
DLGC is a winch-only site, but you can still get 1200 feet plus. The great thing is it is a ridge site, so with a decent westerly and the ridge working you can cruise up and down to regain height until you find another thermal.
Others have already given a good idea of how gliding differs from powered, so I won't re-iterate.
If you decide to do a residential course there, let me know by posting here - I might see you up there!
Enjoy the hush!
SD
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Hoping and praying should never be confused with planning...