Hi Guys,
I'm in a bit of a dilemma.
I have handed in notice at work. Finish on 8 Feb, Start new job on 11 Feb.
I have accepted the new job in writing.
The twist is this. I have just had an email from an old boss at the NHS, out of the blue, offering me a job that I REALLY want, moreso than the one I've just accepted :-/
I would have to go for interview, but purely because it's a "formailty" - the job would pretty much have my name on.
Am I under any obligation to go and work for the company that I've accepted to, if I were to go back to the NHS instead? 
I appreciate it would REALLY mess them around (but I don't need a reference from them!).
Any thoughts? 
It sounds a bit strange that, how definate is the offer, via Email ?, they could always change their mind at the interview stage, and you have no comeback. And if you have just burnt your boats with the first new job, you are stuffed. Also the Civil Service, well..... do you really want to work for them ?. They are always having cut backs, running over budget, and not passing on/loosing medical records. Looking to the future, will it look better on your CV having worked for the Company who offered you the new job, or the NHS ?. Also if you muck about this first new job, they will not like it, and that kind of thing sticks . Experience is a funny thing to quantify, I just found a decent job after best part of a year looking, and its not my 20 years working for large companies that helped, it was purely on one of my hobbies, fixing laptops.
I would also consider which company will give you the most fun in working for.
If all else fails, toss a coin !.
Best of luck,
Ken