I think that if there is going to be a national lockdown, the announcement of it will coincide with the announcement of the approval of the Oxford Vaccine, along with an idea of the strategy for using the vaccine. (ie Vaccinate the 12 - 15 million people who are most at risk of hospitalisation in 6 - 8 weeks, following which restrictions can be progressively eased)
This will give people some hope that there is a way out of this constant cycle of lockdowns, easing of restrictions, tier system, cases going up again, more lockdowns... etc. etc.