Thank you all for your comments. The main driver behind my question was to understand (1) what alternatives there might be to Boris's plans; from those who felt he was wrong and (2) why Boris is right to ignore the advice from the CMO/CSO/SAGE, and the increasing incidence of the virus in places like Catalonia and the USA; from those that agreed with him.
Having read all the posts, it seems most people feel relaxing restrictions is inevitable as lockdown can't last indefinitely. But whilst some express concern about the speed/extent of Boris's relaxation of restrictions, those who support his plans have offered little explanation as to why he is right to ignore the experts.
Personally I believe there is a great deal still unknown about this virus. Emerging evidence is showing the virus is still spreading at pace when restrictionsare relaxed too far, is affecting younger age groups in increasing numbers, and is having a wider & longer term affect on those infected than was first thought, and is not providing immunity to those who recover. For these reason and more, whilst I agree restrictions should be relaxed, I am concerned that Boris's plans go too far too fast and risk the 2nd wave/tens of thousands more deaths that SAGE are envisaging.