Betfair have made the following announcement:-
We are sorry to inform you that due to regulatory changes in the Czech Republic, as of December 21st we will stop taking exchange bets and our gaming products will no longer be available to the residents of the Czech Republic.
You will be able to continue placing Sportsbook bets until further notice. Note all outstanding Exchange bets will remain in place, so please ensure you manage any positions you have open in advance of December 21st. Following this date, unmatched bets can be cancelled but any other changes to Exchange bets will be unavailable. Matched bets will be settled once results have been determined.
If you no longer reside in the Czech Republic and wish to continue betting, please update your details.