I've worked for my current company for about 18 months now. Their primary market is consultancy - we get assigned clients, travel to their offices for the work week (from my experience this is usually around a three hour journey each way), and travel back for the weekend. These contracts are generally 3-4 months to begin with, and are often extended by a similar amount on a regular basis for as much as several years.

I'd had enough of the travel, so I looked for work elsewhere. I found a really promising position, but was also assigned a new client at my current job in the same week as the interview. As things transpired, I got the new job, and handed my notice in on the Monday of my second week with the new client.

Understandably, my current employer is very unhappy about this, and made it very clear that I was putting them in a terrible position. I'd hoped to find a new job before being given a new assignment, but I was a couple of weeks too late.

I've been asked to extend my notice period by a couple of weeks to support a handover period. Normally I'd have been fine with this, but my new employer wants me to start as soon as possible, and due to a number of circumstances (particularly with the holidays coming up), if I did meet their request I wouldn't be able to start the new job until the new year (effectively doubling my one month notice period).

As such I have a couple of questions:

* I know they have no legal right to keep me there, but they've been trying to guilt me into staying for the last few days despite my insistence that I want to leave on the date I gave them. How do I deal with this and get them to accept my decision?
* During the call with HR, I was told that I should have informed the company that I was going for an interview, as this would have influenced their decision to send me on the assignment. Am I wrong for not doing so, given that I didn't want my standing in the company to be affected if I didn't get the job?
* The difficulty with the handover period is that there isn't anyone available to replace me until after my suggested final date. I don't want to leave the company in a bad position, but staying would put my new job at risk before I even start. How can I make my current employer happy in this regard?