Ideally you get the EGR deleted and blanked. Failing that I'd try and clean it to get it working. No special cleaner required, just need to get rid of the soot around the top of the valve head more than anything (the deposits inside the flow path aren't that important in reality so long as they're not completely blocking things, which is unlikely). Obviously if you can't fix it by cleaning then finding a cheap new replacement is the easiest fix. £45 is just for the valve, doesn't include labour if you don't do it yourself.
Shame no one has come up with a simple wiring fiddle to convince the ECU the MAF flow has dropped when the EGR is commanded open. I doubt it's looking for a specific drop in flow, just looking for a step change most likely.