I must say that it's not looking very good for this summer. Greece is now at the highest infection rate it has been, and rising - currently 193 per 100,000. Reuters states that 8.1% of the population have been vaccinated. The vaccination rate is about 25,500 per day. Obviously, these numbers are heavily weighted by the high levels in the Athens-Thessaloniki region, and probably unfairly reflect on the Ionian Islands.
But, in that overall context, given that rates in Continental Europe are worsening, it seems to me unlikely that the UK government will want to open up much before September, if then. Only my opinion, of course, but I think the numbers speak for themselves. The pandemic was spread by air travel, and hence it's not easy to justify opening it up too soon.