dash warning lights on and gauges drop !!

hi i am trying to trace the cause of a fault im having with my 206 1.4 2001 when driving the warning lights come on on the dash and both the speedo and rev counter drop to zero,the mileage disapears and the dash starts doing the oil check, then after a second or 2 the lights go back out and the gauges go back to normal again... any ideas ?? its as if the power to the dash goes off and then straight back on again..

ive had the dash out and checked the plug on the back, checked the engine and body earth in the engine bay, checked all the fuses and checked the main + terminal on the bmi unit

need help please
cheers mark...