Nope, no issues. If there where any legal issues, he is considered as the importer and will face the punishment (you can't fall foul of UK laws unless you're on UK soil). We also have another little presumption in law that you can't actually control what is sent to you in the mail, so even if it is seized by customs he'll just get a nice letter asking him to come and collect it (so they can nick you for possession... that's a lot easier to prove than importing via mail).