How did you find this out? Was it self diagnosis or did the dealer diagnose it?
I realise it's Christmas and hannahh182 is probably busy, but it would be nice if she returned to let us all know how she's going to proceed with this.
Diagnostics on most modern cars can be a headache for most owners. I also think it's more than fair to say, that as soon as an EML light appears, or any other diagnostic notification, owners can often initially go into panic, some owners will go straight to a dealership and get the issue investigated and sorted, and some will seek advice from forums or friends and that can take time and just string out the issue for weeks or months.
By far the biggest issue, are owners that don't want to pay out to get the problem fixed, and there are plenty of owners out there who will absolutely refuse to bite the bullet until they're left with no choice, either because it's coming up to MOT time and the car will fail with diagnostic lights illuminated, or, they will shove the car on and buy another. I was speaking to a mobile mechanic just the other day who doesn't own a garage, just goes out to owners, fixes issues and moves on. Even he said that a lot of the time, he recommends to his 'customers' that they just get rid of the car once a diagnostic issue becomes problematic. Personally, I find advice like that a bit odd.
Dealership diagnostics aren't cheap and I can vouch for that. I once had to pay £60 for just half an hour's laptop time to reset my car's immobiliser system after the previous owner had had it disabled, but once it had been done, I never had another issue with it. I can honestly say now, if I got a diagnostic issue on either car that we now own, I wouldn't muck about, it would be straight to the dealership, I'd pay the cash, get it fixed and get over it. And that would be my advice to any owner out there, if there's a long standing issue you have no idea about how to resolve, stop wasting your time and sort it out.