Testing and isolating are still as they have been, so you need to get a PCR if you have symptoms.
If you get a positive from a routine LFT but don't have any symptoms then you don't have to confirm it with a PCR anymore.
Isolation is min 5 days (day 0 is the start of symptoms or the day you test positive which ever comes first), so:
Day 0 - feel I'll and book a PCR or take an LFT for work or whatever and get a positive.
Days 1,2,3,4 - isolate
Day 5 take an LFT
Day 6 take an LFT
If you get 2 days of negative LFTs in a row you can come out of isolation, or you finish isolation at midnight on Day 10, which ever comes first.
Boris said that isolation would likely end in March, he said this mainly to divert attention away from all his wrongdoings.