The orders are all batched up and despatched either the day before arrival - or if late ordered on the day of arrival. That gives at least 2 days for the tests to arrive at your delivery address via Royal Mail. I think there is a early ordering limitation of 28 days but that is not my bit of the programme.

The test and results process are standard NHS. Nose and mouth swab. Return by priority post box. Results normally within 48 hours of return, sent by SMS and email. No certificate per se.