How many times do we need to reemphasise this? No government, and certainly not the UK one, follows and sticks to a single model or paper. Multiple models from all the best sites in the UK are constantly being rerun and analysed. Governments are going to adjust their strategy every time new lessons and fresher, higher quality data is available. No shit that that will likely save lives. No government in the world, especially those who handle this most successfully, will have done so by selecting a plan early on and then tunnel-visioning into it and not adjusting as necessary.
Nobody, and I mean absolutely nobody, knows all the correct assumptions and input data the models need to get the best solutions. The more confident someone is, the less you should trust them. The authors of the Imperial paper themselves were absolutely clear on that. They too will do future research and, some of which will counteract some of their earlier recommendations. I only hope our government continues to factor that into their thinking. They won't be a u-turn either.