covid 19 – Can I as EU citizen visit the UK in December and January?

I live in the Netherlands and have a Dutch passport. My partner (not married) lives in England and has a British passport. I would like to know what is possible and impossible regarding visiting my partner during different stages of lockdown/tiers. I found Will inbound international travel be affect by the latest lockdown? and How does UK quarantine work for visits specifically to see family?, but my circumstances are a bit different.

I am not looking for loopholes, just want to know what is possbile with the current lockdown or when the lockdown would end. Answers that link to the relevant sections of the gov.uk guidelines are highly appreciated!

My ideal journey would look like this:

  • Travelling from The Netherlands to the UK at the end of December. Going straight from the airport to my partner’s home.
  • Quarantine for 14 days together with my partner. Meaning we both won’t leave the house (having groceries delivered, etc) during that period.
  • Staying an extra week with the possibility to go outside, sticking to the COVID measures at that time (if we are only allowed to go for a walk to the local park, so be it).
  • Flying back to The Netherlands in January.
  • Quarantine for 10 days in my own home.

I don’t see any issues on the Dutch side. The negative travel advice to the UK is only an advice (so it’s not illegal for me to travel to the airport and leave The Netherlands), when I come back I will have to self-quarantine for 10 days.

The questions that I have are for possible situations in the UK:

  • Am I allowed to enter the UK as a tourist during lockdown? Or when the lockdown ends and Tier 3, 2 or 1 are in use?
  • Am I allowed to travel from the airport to my partner’s house during lockdown? Or when the lockdown ends and Tier 3, 2 or 1 are in use? Don’t know if this counts as one of the specific reaons for which travel is allowed.
  • Am I allowed to quarantine at my partner’s house if my partner goes in self-quarantine as well?
  • Are there legal Brexit limitations when I stay till January? Practical issues like roaming or adjusting my travel insurance can be easily overcome, but if I’m illegal without a visa that would of course be a problem.