Default Data connection keeps stopping - Three UK

Over last few weeks i noticed that my data connection keeps dropping and i cannot connect to any website or anything.
I happens probably once every 10-20 mins but it shows i have full bars and H sign still there but nothing will connect or my tv streams stop working etc.

Only way to fix is either reboot or switch mobile data off and then back on again and then it starts working again after a minute or two. Its driving me crazy because i cant watch any live tv or browse the web properly.

Im stock rom not rooted my phone or anything - any help would be greatly accepted.