Now that the EU-UK Trade Agreement is finalised, and due to be signed, this new thread is about self-build in the new environment.
There is a decent summary of the agreement here: at the Institute for Government, which has both the salient points of the agreement and an interpretation in human-ese:
https://www.instituteforgovernment.org.uk/publication/future-relationship-trade-deal
We will keep the focus a little (!) more tightly on self-build than the previous threa