My VX developed a problem afew weeks ago where as when it was idling (traffic lights etc) or going below 15mph the revs were constantly fluctuating casuing lack of power and very bad fuel consumption. see the video below:
Idling Video
The car felt like it was going to stall at any minute and trying to start the engine turned into a nightmare. I initially thought it may be the spark plugs, so i changed them with brand new ones, only to find it had not changed at all

After spending 2 days searching the scrapyards, i came across a 2001 Vauxhall Vectra so i took the valve off that. (it is also the same from the 2.2 Astra and Zafira) Just make sure its from a Z22SE engine! Mine was £24

Here is a basic guide on how to replace it:
First undo the two bolts either side of the valve (one side shown here):

Then remove the plug from the top (There is a small plastic 'catch' on the inside of the black plug at the top):

Then the old one is out, the gasket underneath can be re-used for the next one:

Here is the EGR valve and gasket:

Then once you have the replacement valve, just do the reverse!

10 mins max!