Obtaining Domestic Travel Insurance During Covid-19

We booked a holiday cottage in the UK for the end of July 2020. We neglected to purchase travel insurance when we booked it at the start of 2020 (we've learnt from this mistake). We have already started paying the balance on this trip.

So now we are looking at purchasing travel insurance but we are concerned that the Covid-19 lockdown currently in the UK, will invalidate any insurance we take out now. The optimistic estimates put the end of the lockdown around the 15th June.

Is it worth us taking out the insurance now to protect our existing deposit/holiday or is likely that all insurance policies purchased now will be invalidated if there is an extension to the lockdown?

Any guidance on this is much appreciated.