I reach that conclusion because there is no discernable significant change when the variant is thought to have first occurred here and there have been much bigger changes around the time of each control policy change; the same appears to be true in the other countries that I've examined fairly closely; so I do not think presence of the variant is the dominant difference between the UK and other nearby countries.
We might not have had the highest cases/100,000 of any of the countries in the "big countries" graph at any time in the September-November period, but we never had the lowest either and once the shoot sandwich of "unlocking for Christmas shopping" and vacci-mania hit, that high base level provided a springboard.
Yes, everyone here has zero qualifications or experience, except for those of us who are qualified in statistics and have worked with health data (although I didn't do it for long before detouring into IT and it was many years ago now). I sometimes make mistakes but often someone will point it out and I'll say I was wrong, narrow my conclusion, or say that we can't know which interpretation is correct and mine obviously isn't the only one.