Just thought I would post here because someone gave me this advice before I travelled in September and it really was good advice.
Would recommend you print everything off to carry with you because when I travelled in September the queues were caused by people with apps. Anyone who had everything printed off got through very quickly.
So boarding passes, NHS COVID-19 Certificates, negative PCR tests, entry forms for the country you are travelling to.
Hope that is in some way helpful.