Theoretically, yes, you will need an MSc BUT exceptions are made in London for people such as yourself. I would recommend you look for a "Research Technician" post which allows PhD study alongside it. You won't miss your current salary and they will be more interested in your skills rather than exambased record.
If I were allowed to overhall PhDs, I'd stop the 2:1 entry requirement. Some people with amazing U/G project work get 2:2s and a lot of 1sts are inept in the lab.