Looked at this again today and checked wiring from sensor and leak off pipes etc and all seems ok and its starting ok now.
Spoke to a guy i know at local vauxhall dealer and he said there is an air mass flow meter fault that causes this kind of fault i.e poor starting/no throttle for 10-20 secs but i scoped it and it looked ok as it peaked just under 5v.
Still not sure why i was gettin 1.1v KOEO from frp sensor. Is there anyway off testing the relief valve on end of rail?
You should check the duty cycle values of the rail pressure regulator. I've found some data that may help you in diagnosing the DRV valve - it´s from a Renault Megane II with a F9Q 816 engine which is very close to a Trafic engine.
With the engine running and the engine coolant temperature > 80°C the duty cycle should be between 35 to 45 %
With engine off and ignition on - the value should be equal with 15 % duty cycle.
I fitted a new OE air flow meter and the starting and throttle repsonse from start up has noticeably improved so customer has taken van away to try it.