I think a lot of people are missing the point of the whole govt strategy to fight coronavirus.
The strategy is not to eliminate transmission completely, it's to reduce it to manageable levels. By manageable levels, i mean manageable for the NHS.
The govt will be 'accepting' a certain spread rate as 'okay'. That spread rate rate is what is manageable for the NHS to deal with. It's like banks who assess their 'risk appetite'. Sometimes any risk is unacceptable, and will look to eliminate it entirely. Other times, banks will assess that a certain level of risk is acceptable, and not look to eliminate it further. This is how the banking industry works ultimately. A lot of the time, you will never eliminate it entirely, or to do so would cost more money than you have, so you just eliminate it as much as reasonably possible etc. This relates exactly to our situation here. A transmission rate of X is what the NHS can manage, so this rate is our 'risk appetite'.
As soon as it looked like it was becoming unmanageable in the NHS, then they put in the lockdown in March/April. Then as it looked like it was becoming more and more manageable, as hospital admissions figures went down, then they loosened up the lockdown. Then once it looked like it's becoming unmanageable again in some areas they put in another lockdown, before putting in a national lockdown as figures started to rise quickly. As I say, the key word is 'manageable'. It's all about keeping it manageable for the NHS.
So it's a matter of what will keep the levels within our 'risk appetite'.
They have gradually opened various amenities, in order to open up the economy or to bring back education, and all of this will be done with the knowledge that all of it contributes to the ultimate transmission levels, and all of it raises the level closer to the accepted 'risk appetite' figure.
IMO anyone suggesting an outright ban on Xmas gatherings, should also be against the opening of all bars, all shops, any sports (and stadiums), and probably most importantly, all schools. All of these will have effects on the virus spread rate.
As I say, all of the things they have opened up will have a risk factor associated with them. It's just about which risks do you 'pick' at different times. At Xmas obviously the social side is very important. So far they've been pretty stringent on the social gatherings side.
I see no reason why we can't have less stringent rules on social gatherings, at the expense of other restrictions being more strict. With the aim being to keep the rate within the manageable boundaries - not reducing it. That said, i wouldn't want another month long lock down. This one is a nightmare. I would hope there's other things that could be done.