Help. I Don't Know What to do...

Mondeo 2.0 Tdci Zetec S 53 Plate 71000 miles

I hope you can help me out here. About 6 weeks ago, I had a situation where my car wouldn't start and I had the flashing glow plug light, a situation that worryingly crops up frequently on forums. During the following week, the car would start OK but then would lose all power and stall while I was driving. As I travel through the Mersey Tunnels twice a day this was extremely stressful as I did not want to stall in the busy tunnel. I rode my luck a bit and had stalls just before and just after the tunnel.

Took the car for a diagnostics at a back street garage in Liverpool and they said the only error code showing was the Camshaft sensor. I replaced this and it has been absolutely fine for the last 6 weeks. Until last Friday that is. Driving to work, it repeatedly lost all power when trying to accelerate when joining the motorway and this must have happened about 8 times before I managed to limp home. This has repeated every day since, even when not accelerating hard. Only yesterday, coming out of the tunnel, in 3rd gear doing just under 30mph the engine again lost power and stopped. Luckily, I was 100yds out of the tunnel. As a consequence, my stress levels have increased again.

Another diagnostic test pointed to an Overboost in the turbo wastegate ? I'm no mechanic. I do have the Haynes manual which always makes things sound so easy, but in reality I know they are not. But what could cause an overboost. Does the EGR need a good clean out. Or could it be a faulty turbo.

What to do? Do I go to the main Ford dealer and risk paying through the nose for possibly unnecessary work. But I don't know any other garages who specialise in diagnosing and fixing the problem - there's nothing listed in the yellow pages. I could just end up throwing good money away trying to get it fixed, so should I trade in the car for something else ?

Any help or advice would be appreciated

Thanks

Baz