It is very difficult with the Czech channels on 23.5E and dish quality/alignment is critical. I can't comment on the quality of the dish, as I've never used one and it is quite difficult to get hold of quality 1.2m dishes in the medium price range from the wholesalers.
One of the best of the mid range dishes is the Gilbertini 1.2m, combine that with a matched C120 feedhorn and 0,.3db LNB and you should achieve solid reception, but they are difficult to get hold of at the moment. Channel Master/Andrews make a superb 1.2m dish, but it is top price band and once you've bought the feedhorn, LNB and AZEL mount, most people think it is too expensive.
There may of course also be external factors influencing the reception, even down to cell phone masts or DECT phones, perhaps local radio operators.