I don’t think there’s any way of knowing specifics in terms of how many could have been saved, so saying half is incredibly harsh. The pandemic is also not over, with our vaccination programme being several times quicker/bigger, the difference in figures at the end may well be much shorter.I think it would be not unreasonable to expect our figures to be no worse than Germany's. They had the added disadvantage of being on a landmass containing 80% of the world's population with easy access to 500 million of those 80%. Our population density, at least in England is higher than Germany's yet there are areas of Germany with equivalent population densities such as the Rhine-Ruhr area, so overall population density shouldn't be a significant factor. The benefits of being an island nation and theoretically having better control of who arrives (although we chose not to) should more than have compensated for differences in population density. In summary I would say that the government have been responsible for the pandemic being twice as bad as it needed to have been in this country. No way to prove it one way or another - just an opinion.
Regarding Germany specifically, isn’t it true that they have also been stricter with their Covid death figures, in that there will be deaths there not counted, that would be here?