I hope this is all academic and everything is sorted already, but it is not usually in your interest to take another job whilst negotiating a severance package. A tribunal would take your new earnings into account when estimating your losses following a sacking.
That depends on whether your objective is to get as much as possible out of your former employer or to get another job! Either way you're earning money, and I'd suggest it's better in the long run to be employed.
And everyone I worked with thought that HR was easy! Obviously not. Without seeing the actual contract, I've honestly got no idea what they can enforce or not. What I would say is that some clauses are put in which aren't actually legally enforceable anyway (they would have to be within the law to start with). That said I can't see why anyone would want to stop NA from working and I can't imagine any such clause.
I had a clause in a contract banning me from working for opposition for a year (I think), but, as said above, I suspect only enforceable if I left voluntarily. You can't really sack someone and then ban them from getting another job. I suppose if they pay Nigel they could insist his job is staying at home, but can see no reason for that. Nicola doesn't hate Nigel, he made a business decision. If it's not sorted already, I suspect it's just a matter of dotting a few 'i's and crossing a few 't's. Nigel is just taking his time and who could blame him.
I would have thought that banning someone from working after you have sacked them counted as restraint of trade, which would mean any tribunal would find for the appellant, i.e. the manager who was sacked. I agree with Fran, this isn't likely to have been the case with Nigel and he's just having a break until the end of the season and see who comes calling then.
I think Nigel should just attend as many matches as possible...just to wind up other managers, especially if televized so the cameras can zoom in on him. Perhaps he should ostentatiously take a few notes at the same time.