Thanks very much for all your replies, it really is appreciated.
I cleaned the EGR valve out a month or so ago and it didn't make any difference 
.
Today, I disconnected the connector that goes onto the MAF sensor (at the back of the air filter box) and it wouldn't even run...
Spruce, if I blank off the EGR, what would I do with the wiring? I've seen a tutorial online http://hubpages.com/hub/How-to-remove-clean-or-bypass-an-egr-valve-from-a-trafic-vivaro-primastar-diesel-van so that maybe an option...
Also, looking at a couple of forums, there is a thing called a boost pressure solenoid, that has a couple of tubes going to it that could be blocked..
http://www.honestjohn.co.uk/forum/post/index.htm?t=62080
Anyway, it failed the Mot today on a wheel bearing 
so once that's fixed, I'll be back on it!
Thanks again boys
Dave
I see that they use a different method to 'blank' or stop the EGR valve from working.
He wasn't very clear about the wiring but in the comments from the readers it is mentioned that the wiring goes back as before. The ECU will be fooled into thinking that everything is working correctly. Apart from that the instructions seem quite detailed and straight forward to follow.
The wiring was one of the issues when people removed the EGR valve completely. The ECU recognised the problem and flashed the engine management warning light up. It was annoying but drivers soon got used to it if they thought about the benefits. However, if the management light is on when the van is MOTed then its a fail. You can't take the bulb out either - inspectors are looking at the correct sequence of lit lights going out.
One some vehicles it flagged the limp home mode.
On the hdi engines it is just a flat plate which blanks the EGR valve at the manifold. As there is no component past the flange, that blanking plate works fine with 1 new gasket. Again wiring is left connected to the valve.
Despite the comments, the EGR valve has nothing to do with warming the engine up quicker. It was only introduced by the manufacturers to reduce NOx. Diesel emissions aren't tested at MOT although they do a smoke test which is a different thing. The EU made it the motor manufacturers responsibility to make sure each new vehicle achieves the latest emission standards. Blanking the EGR valve off actually brings the engine temperature up quicker as the combustion intake is now 'pure' and not contaminated.
Just always be living with the thought that there is every possibility that diesel emissions could be introduced into the MOT test as it is for petrol engines so you will have to return the EGR valve back to its original state.
Of course there is nothing stopping you changing it back after the MOT test.
Added:
If you do blank the EGR valve then you could leave yourself open, as messing with emissions is an offense. The new stance taken by the DVSA (replacing VOSA and DSA) with regard to DPF filters is going to set a precedent for cataylitic convertor removal etc. DPF inspection is part of the MOT test from Feb 2014.
https://www.gov.uk/government/news/new-rules-for-mot-to-test-for-diesel-particulate-filter