I refer you to Inghams' Ts&Cs from their website for next season's ski holidays;
BREXIT AND ITS CONSEQUENCES:
[…]
At present, the Changes in Law [as a result of Brexit] that we consider are most likely to occur and, in turn, affect your chosen arrangements are as follows:
a) A potential inability for the United Kingdom as a whole (and ourselves, for the purpose of this clause and your chosen arrangements) to rely on the free movement of workers and, in particular, the Posted Workers Directive. The result of this may be that we are unable to provide you with certain services that make up your chosen arrangements, such as the provision of a local representative, chalet staff, etc.
b) A potential inability for British airlines to operate flights into / out of the European Union and, conversely, an inability for European airlines to operate into / out of the United Kingdom. The result of this may be that we are unable to provide you either with the flights that you have booked or indeed any replacement flights.