uk – How long to book a quarantine place if using test to release scheme

I booked a self-isolation place for 10 days for my trip to the UK. Due to some circumstances, my plans are postponed by 5 days. I made some bookings in UK after my 10 days isolation was supposed to end. I can not cancel/reschedule these booking.

I found out about the Test to Release scheme where I can take a test on Day 5 of my arrival in the UK and can end my isolation if that result is negative. This would work perfectly for me as my trip is delayed by 5 days and I would be able to attend my other bookings.

Now my question is how long should I book a quarantine place before I travel to UK, should it be for just 5 days or 10 days? I prefer Airbnbs over hotels and no Airbnb provide any cancellation benefits during the middle of your stay.