Thank you @jojojo and @PennaThere's a rule change expected mid-May. Hotels, restaurants etc reopening. There's expected to be a change in the rules on travel at the same time.
The question will be will be - are there quarantine requirements at either end of the trip, and what tests are needed. All still up in the air really - but the end of May is a possibility. Provided they can cancel/postpone, I can see why they might want to start making plans.
There's a good chance that family visits will get priority from the UK side over general tourism. It's all anybody's guess though.