You can, the new job has no bearing on the treatment by your current employer.
However it's almost impossible to win a constructive dismissal case if you work out a notice period - you basically have to just quit and refuse to go back in to prove that the conditions were bad enough to be constructive dismissal.
Yes.
You may get sacked, though.
That applies only to a loss of earnings award.
Any compensation award on other grounds would be unaffected, so if John argued any form of discrimination (for instance) he would receive an amount of compensation for that which is separate to the calculation for loss of earnings (discrimination claims have no upper limit. yay discrimination!)
It used to be the case that the reason for leaving had to be entirely because of the constructive dismissal, but the Court of Appeal ruled in Nottinghamshire County Council v Meikle that the constructive dismissal only had to form some part of the reason for leaving - hence why John can jump ship to another employer and still claim constructive dismissal.
That's not to say he'd win, of course. Constructive Dismissal is a right bitch to prove.
In order for the contract of employment to remain enforceable, yes.
No obviously the main part of the contract (i.e. going to work) is coming to an end anyway, so you wouldn't lose out much on that front. But there are other parts of the contract which you would lose out on, such as payment for holidays you have accrued but not taken*.
Also any benefits which might have a run on period, like private healthcare, or any other perks that remain after leaving.
Basically if you don't give notice you have breached your contract and have no right to receive any of the benefits of it**.
(*Anything above the statutory minimum, anyway)
(**except for payment for the work you have done up to the point you bugger off)
Also, it's just fucking polite :@
This is actually really helpful, if anyone else can think of random questions I'd really appreciate it. Although I *think* I know the answer to most of these, it's useful to be prompted on a subject so i can check it and see what's changed in the last 18 months or so since I went mental.
Depends on your contract. Also, your employer doesn't have to give you any specific days off and can in fact tell you when you're off instead.
The law only says you have to have a minimum of 5.6 weeks off a year, but not when you get them :(
5.6 weeks? Really? A lot of places only offer 22 or 23 days. Though it would explain why the NHS have generously given me 27 days holiday this year.
Or are you including public holidays? If you are, then the NHS are /really/ generous.