Thanks guys, I had been wondering about leads etc, but the leads are new, as is the dizzy cap. Could be the coil I suppose. When it did it at speed it felt like misfire, but when setting off its not quite the same.
Really annoying me now.
With all of the work I have done recent almost all of the things discussed above were affected, so I cant really pinpoint where my poor workmanship may have messed something up.
The front mount was undone to replace the starter.
The lift pump was removed when dropping the tank
The leads and cap we all replaced when they melted in a fire.
Almost every vacuum hose has been replaced
The plugs were taken out, cleaned, and put back in, not replaced though.
The injector rail was removed and refitted as the loom as damaged in the fire. Injectors were left in though.
All of the above was done at the same time. And it drove fine until about 500 miles later :/