If it is a cold approach through someone contacting you on linked in, facebook or similar start by making sure that they are registered for data protection act purposes in the UK (there’s an online search tool on the ICO website).
I have had a couple of approaches from seemingly legit operations who with a bit of research seemed more likely to be chancers trying to get hold of personal data etc. They tend to go quiet when you start asking questions about stuff like dpa registrations if they are not legit.
Also if they are a UK company check they are registered at companies house and they’re up to speed on accounts etc and the size of their business.
I gather there are a number of scams around overseas job offers.
I am not suggesting this particular company is not legit by the way just saying make sure you cover your back side before you give to much away.