my boyfriend who is a non visa national from Argentina is coming to work in the uk on a tier 5 sportsperson visa sponsored by his work next month. However he wants to come before his work visa starts as a tourist. He doesn't need a visa as a tourist and can stay 6 months. Question is can he enter UK and get his visa stamp at the the boarder and then have his work visa processed whilst still in the UK , or does he have to go back to Argentina to re enter on his work visa? Also does he have to have his return ticket booked. Because he is technically allowed to stay 6 months as a visitor but his work visa is for 1 year, if possible he won't book a return journey as it will be in a years time and after he has to return on a tourist entry. 

Any help much appreciated.