"The EGR valve helps your car more efficiently and completely burn fuel by recirculating a portion of your exhaust and running it through the combustion process again. This results in a cooler, more complete burn of the fuel which decreases you car's noxious emissions by prohibiting the formation of some harmful gases."
As a result, they get carbon'ed up and stop working, causing rough/lumpy idle and revving. By doing this you are by-passing the EGR valve.
They can be replaced, but are quite expensive, so after this thread and some googling I found you can blank them off. Vauxhall actually sell EGR blanking plates for some cars!
I tried the coca-cola (well Dr.Pepper tbh!) methold for a quick test..
Get a drink's can and consume the liquid goodness!
The EGR valve is hold on by 2 x 10mm nuts..
Remove it and make a template using the original gasket.
And re-fit! Simples
After doing this, the ECU was still on but revving up and idled and lot better than before, but after a long run the ECU light went off and has stayed off.
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EDIT : Leave the EGR connected/piped up too!