None of those quotes say they aim to create herd immunity. They just say you won't get herd immunity until about 60% are infected. There's a difference.
Patrick Vallence:
> ‘So our aim is to tray and reduce their peak – broaden the peak – not to suppress it completely. Also, because the vast majority of people get a mild illness, to build up some degree of herd immunity as well.
https://metro.co.uk/2020/03/13/millions-brits-get-coronaviru...
Herd immunity is a direct aim of the current phase of the government plan -- it has to be, because they think that covid-19 will become a seasonal illness.
https://www.ft.com/content/0475f450-654f-11ea-a6cd-df28cc3c6...
> The prime minister and his scientific advisers hope to manage the epidemic by “flattening the curve” of infection and delaying the peak until the summer, when the National Health Service will face less seasonal pressure.
> Then — or so the theory goes — enough people will have acquired resistance to Covid-19 to avoid a second wave of disease next autumn or winter. Downing Street believes that other countries that have taken draconian action now will be vulnerable later in the year.
> Mr Johnson’s strategy depends on building up the so-called herd immunity. If a high enough proportion has become resistant through Covid-19 infection, the virus will not have enough new people to catch and the epidemic will not be able to sustain itself. It will burn out.
But even this is wrong, or at least, unsure. Herd immunity relies on low (or zero) re-infection. It works for diseases like measles, where the risk of re-infection (after either infection or immunisation) is effectively zero.
We don't yet know if re-infection with covids-19 is possible or not.