the previous answer is totally misleading. companies will not put you through your offshore ticket, there are that many people looking to go offshore that they can pick and chose who they like, unless you are from a specialist company that the main operator needs because they are losing money through equipment failure etc.
there are not many offshore positions available without a trade, i.e. plater, pipefitter, rigger, scaffolder.
the only way i can see you getting offshore with your skills is to contact the major service companies who carry painters and try for the shutdowns. this gives you the foothold into the offshore game, BUT, you will have to pay for your own R.G.I.T. ticket, currently around £750 and your medical, around £90. its a catch 22, no experience and no ticket or pay your own and hope for a shutdown, sorry. it would help and get you more opportunities with a rope access ticket.
try a google search for offshore employment agencies, also try SALAMIS, and RBG (RIGBLAST), those two carry painters on their books