For some and I am sure there are some nerds in IT who have created a script (or whatever) that picks that up.
When a mate went it to collect his winnings on the Euromillions (over £50k you have to go in to their office) they asked him to log in to his online account (he did not have sufficient ID apparently). Initially it said he was outside the UK (he was at Camelot in Watford!) and the IT bod, who was sitting opposite him, asked him if he used a VPN and if so to turn it off. He then asked why the timezone was for Bejjing. My mate explained that he used online gambling sites and changed his timezone to wherever the platform was based (he did explain why but I forgot).
So yes, they can tell especially if you are actually outside the UK.
The IT guy said it had flagged up before that when he logged it the timezones were all over the place!