I tried google but all the links I found were in czech. Can someone give
me some hints of good clubs to fly in the czech republic at the end of
august. *English or french site would be helpful

If you will be near Prague, try Benesov, LKBE airfield,
http://www.minfo.cz/benesov-info/zi_informace.php
web page is in Czech only, but Bene Info 118.000 communicates also in
English
(not always common on other sites).

There is professional gliding school here,
http://www.aero-gac.cz/document_root...on=nabidkaletu
with some gliders for rent,
currently 5x VSO10 (performance similar to ASW 15), Twin Astir,
Blaniks, Dimona,
often also ASK 21 for aerobatics.
Contact school chief/owner Milos Ramert mentioned in Contacts if
interested.
Thermic weather near Benesov is usually one of the best in CZ,
and GAC school flies everyday, if weather permits.