Agree it's stressful getting through the airports, but worth it if you want to get abroad, which itself can be very good for your mental health.
A few tips
The airport staff are likely to check your paperwork both ways, and they have the power to stop you boarding so get everything ready. On the way out, it's just the vaccination barcode, either on a phone or on paper. Not the card. On the way back you need results of an antigen test, a locator form, and the code for your day 2 PCR test. The checkin staff may ask to see the invoice from the PCR test even though the number is in the locator form. Also one thing that caught me out was the rules say the antigen test must be "in any of the three days before the day of the flight", but the checkin staff refused to accept one that was 72.5 hours before but within the clear rules and made me get another one.
You can buy a self-administered antigen test in the UK to take with you, that you then do over video link and they send you a fit to fly certificate. This is less stressful than finding a test centre if there isn't one at the airport, but more expensive.
Don't worry too much about the horror stories about test providers for the day 2 test, just go for the cheapest. It's a paper exercise - they phone and ask for your result, and if you say "it's not arrived yet", that's fine, the box is ticked. The company I bought my previous tests from were exposed as dumping the samples and giving people a negative result or nothing. Test and trace didn't care (and in the end I got the money back!)