As many as 2,000 Czechs are believed to be stuck in London due to the recent snow storms that shut down the four airports from which one can fly to Prague or Brno (Heathrow, Gatwick, Luton, Stansted). Prague is served by EasyJet, British Airways and Wizzair
and Czech Airlines (Daniel Duda noted that CSA does not serve Heathrow as of November 1 -ed), while Ryanair and Wizzair operate flights to Brno.
There are limited opportunities when it comes to ground travel: according to the reservation system of Student Agency (major Czech operator of international bus lines) seats are sold out through the Christmas Eve. Eurolines has a few seats left for December 23 (as at Sunday at 10:50 p.m. CET). Naturally, most Czechs who are in the U.K. now are on low budget and cannot afford staying in a hotel voluntarily wait until departures are resumed.
Of course, the flights between the Czech Republic and the U.K. are significantly disrupted by the fact that some planes had to stay in Prague (or even in a different city while making their daily roundtrips around Europe), so they will not be readily available at Luton or Stansted.