Right, finally fixed it and you won't believe what it was. The fuel line from the tank to the rail had collapsed and was restricting the fuel. The pipe had a protective plastic coil round it so i couldn't see the damage.
The bike is a 98 TLR 25000 on the clock and it has been a little neglected by the previous owner.
Not many mods at the moment but I have plenty of time to work on that. Thanks again for all the help. It's nice to know there's a good bunch of lads willing to lend a hand.