ok guys, went out this morning before work and took rad cap off and the radiator was full and so was overflow tank.. so i started the car up and the coolant started to rise and come out of rad, so i closed the rad with cap, emptied the overflow to just about low and then went for a drive... when i came back the overflow tank was full. left it there for about an hour and it was still same... phoned the place that did the conversion and they suggested i do the same thing and empty the overflow tank, fill the rad up and go for another drive but dont boost it and i did that... went on to the motor