MY MACBOOK THINKS THAT I AM OUTSIDE THE UK, HOW DO I CHANGE IT

I FREQUENTLY TRAVEL ABROAD, FROM THE UK. I OFTEN USE A VPN (STREAM VIA) TO ACCESS GEOGRAPHICALLY RESTRICTED SITES. I STILL COULD NOT ACCESS A UK TV SITE. BACK IN THE UK, I HAD TROUBLE ON A FREQUENTLY USED SHOPPING SITE WHICH THINKS I AM OUTSIDE THE UK. MT IMAC SITTING ON THE SAME DESK HAS NO SUCH PROBLEM. HOW DO I RE-CONFIGURE MY MACBOOK TO RECOGNISE MY ACTUAL LOCATION.