We will be having an overnight at LHR airport and know we’ll need an ETA. Are there any ETA issues we should be aware of? Thank you.
Only use the official website and app to get one: https://www.gov.uk/eta Anything that charges you more than 20 pounds is not the official site. Some people have issues with the app reading passports and taking photos. Do a quick search in the forum on "ETA problems" and you'll see where things have gone awry.
I have seen very few posts about problems in getting an ETA for several months now, which suggests that the system is working pretty well. As CL says the main issue is people clicking on a commercial site rather than the official UK Government site and thereby spending much more than they need to.