Thank you for the advice guys.
One small note though. I already live in the UK, but have had to leave the country to oversee a sick family member for a few months.
I only drove back to go and do the sim, but I will stay in the UK until the flying starts again.
Am I right in saying I don't even need to quarantine since I live in the UK?
I ordered the day 2+5+8 test regardless. You never know which intrepretation of the rules will apply to a "grey area situation" like a sim.