At the moment booking holidays is extremely risky. It's impossible to know if and when a new covid 19 lockdown will be imposed, or which countries it'll be safe to travel to from one week to the next. Having waited nearly three months for my refund when my Porto trip was cancelled in March I know trying to get money back from companies really isn't as easy as it should be, even when the government has banned all but essential flights. Thankfully some travel companies are starting to realise that the only way they're going to make people feel safe about booking a trip is to offer free cancellation.
Expedia are offering free cancellation on most hotels across Europe and the UK via this link. I should say that this offer comes with a health warning, it only covers the hotels so my advice would be to either stay in the UK, or book the hotel and make sure you book the flight on a credit card. By using a credit card you can claim the money back off that if the airline tries to mess you around with the refund so you'll still get it in the end. I'd also suggest finding somewhere with nice cheap flights. Copenhagen, Prague, Dublin and flights to Germany, Italy and Spain tend to be reasonable. I've actually done a couple of those for less than £40 return flights so even if you do have to wait a little while for the refund it's not the end of the world.
Hotels.com are offering pretty much the same deal as Expedia but with the added bonus of 8% off with code AFFGEN620 if you use this link. The offer only runs through to 05/07/2020 but covers hotel bookings all the way through to March 2021.