davidjohnson6 and kcockayne, the Civil Contingencies Authority of the States has announced that it will re-introduce country and regional travel categories from 23 April
https://www.gov.gg/reintroducecategories
Reading between the lines it is likely that for the moment most or all of the UK will fall into Category 2, reintroduced on 14 May:
It is the CCA's current intention that from the 14th May, 'Category 2' destinations will then be introduced. Broadly, category 2 will apply to destinations with a prevalence of below 30 cases per 100,000, which also satisfied other Public Health criteria. Category 2 travellers will be tested twice, on arrival and on day 7, but they will only need to self-isolate until their first result comes back negative. They can then leave their self-isolation and observe 'passive follow-up' rules until 14 days after their arrival.
So most travellers from the UK will likely have to self-isolate for 18-36hrs (depending on the time it takes to get the PCR result back), paying £25 for each test. Hardly an entirely straight-forward exercise but equally probably less onerous than much of the world, so we can expect a reasonable up-tick - and presumably as airlines hear of the new rules, some confirmed dates for summer '21 ops.