Dan, regarding your benefits should it come to this, as you quit you will not be entitled to claim normal JSA for quite some time.
However, what no one tells you is that you can claim "contribution based JSA" this is based on your national insurance contributions over the last 2 years, regardless of any savings you might have. Im not sure if you can claim this immediately. I was very ill when i quit my job in Feb so couldnt deal with something as simple as that for quite some time. Get down to the CAB if you think you may be out of work for some time. £71 a week is better than nothing. Though it'll obviously be a massive reduction in your disposable income if your out of work for a while.