Under the July 2018 Package Travel Directive, travel firms offering package holidays are legally responsible to provide either an alternative holiday / destination, defer or change travel dates or offer a 100% refund if they have to cancel or cannot provide travel service due to Foreign, Commonwealth and Development Office advice / travel restrictions.
You will therefore should not suffer any financial loss if you have purchased a package holiday to somewhere which has been placed under UK government restrictions due to coronavirus, and should contact your tour operator / travel agent in the first instance.