Given there are no restrictions at the moment, I doubt the UK would go fully into lockdown within weeks
But this is absolutely what has happened in many places in Europe, so it is a completely reasonable question.
As noted vaccination rates are broadly similar, so vaccination is not a difference.
What is a difference, is that the UK has had 4 months of over 1% a week positivity, so that's 20%+ of the population protected also via recent infection, The European countries locking down do not have that, and with only the low quality mitigations they need to lockdown (the only effective mitigation is lockdown, masks might be effective at reducing but only in situations where you are masked, as soon as you eat indoors, that's gone as a successful mitigation) they are far away.
With vaccination being poor at preventing infection, their "3G" systems have been particularly found out, as letting in vaccinated people who can spread it without testing just provides a route to infect all the unvaccinated who are also allowed to attend - the testing of unvaccinated only achieves little. Encouraging testing of everyone (as here) makes more sense - it doesn't prevent spread of course, there's nothing been shown anywhere to work other than lockdown to do that - but it does spread it out.
If you remember from the very first wave "flattening the curve" is the aim, so the UK has had a very flat curve over the last 3 months, but many European countries have not, they now have an explosion in cases, particularly as the weather also likely provides a transmission advantage to covid that wasn't there earlier in the UK.
So in terms of this wave, the UK is almost certainly "ahead", not behind. Of course, that doesn't mean that the next wave isn't going to be worse by the UK having an earlier one - making the mistake of comparing "instants" between countries has been done way too much.