We travelled back to the UK on Sunday night (18th July) through Schipol via KLM.
No issues. Just needed our negative test and PLF at check in.
These were checked again before being allowed to board the final flight to Newcastle, but, again, no issue.
Not sure if any of that will change when Netherlands put Thailand on their Red list on the 24th.
It shouldn't do, but best to check with them.
If you're travelling through Dubai, you'll need to book a quarantine hotel before you travel.