ESP light stuck on!

My ESP light has come on today and refuses to go off! Pressing the button has no effect at all. Now, the thing is the service dept at the dealers was shut this afternoon and it obviously not open tomorrow, so it will be Monday before I can take it in at the earliest...
BUT: My warranty runs out tomorrow!!!!

I phoned up the dealers this afternoon but could only speak to sales (as the service desk was closed). I asked him to log the fact that I had called with the problem today (ie, before the warranty runs out) which he said he would do. So, I intend to ask them to repair it under warranty seeing as the fault occurred whilst it was still covered.

What do you think my chances are?

Cheers, I'll stick that in my mobile. They have generally been fine with me in the past and the guy on the service desk (unfortunately!) knows me quite well from having it in with numerous problems in the past! I've always had my work done with them (bar the last service which I had done at another dealers simply for convenience) I should hope they won't be arsey about it especially seeing as I'll be taking it there for all future services plus four new tyres in a months time (well, so long as they fix this under warranty anyway! )

Anyone any idea what it might be? I did try slamming on the brakes on my way home tonight (on a quiet straight country road and at a low speed!) just to try and get the ABS to come on - which it did. So, I don't think that is completely buggered.

On the wet drive way tonight I did a it of an experiment made it wheel spin so the traction control is definitely not working!!
Could it just be a sensor or is it likely to be something worse?

Ye I suppose so, but you would think after the engine had been switched off over night it would have fixed itself if so. I hope I don't get the usual 2 weeks bloody wait before they can book it in!! I might play the "it's a safety issue and the car is unsafe to be driving in as it is" card...

I spoke to them today and they said they will get it in on Wednesday (earliest it could be because they are collecting it) and they will back-date it on warranty. May as well get them to look at it if it's still covered, just in case it's an expensive job!!!