Hi all thought I would post our experience incase anyone else is looking for information going forward.
I'm a British citizen and Canadian resident.
Partner is Canadian citizen.
We travelled to England before Christmas from Canada.
We caught covid-19 and got positive PCR results through the NHS.
Travelling back to Canada we waited until 14 days post positive test and then filled in the ArriveCan app stating we had contracted it over 14 days ago.

In order to board in London at checkin we showed the NHS positive result email (I showed the staff my recovery NHS Pass but they wanted to positive test result for the date) as well as our arrivecan reciept and passports.

We were never challenged to see anything more than boarding passes and passports on the UK side beyond this point.

Upon landing we showed our passports and resident cards. Nobody asked to see any other documents other than the mandatory customs declaration.

I hope this will help inform people and calm any anxiety for travellers.

It really couldn't of been easier.