With regards to Jazzer's legal claim, I'm not a practicing employment lawyer but I do have some experience of employment law.
I think Jazzer and Jim are on thin ice with a constructive dismissal claim. CD is phenomenally difficult to prove which is why I find it surprising that an employment lawyer would have said he had a strong case as in my experience they tend to steer away from CD unless it is open and shut.
In order to prove CD you have to demonstrate that it would be untenable for you to continue working for your employer in circumstances engineered by the employer to effectively manoeuvre you into leaving. This might be something like transferring you to an office at the other end of the Country at a moment's notice or making you work with someone who has bullied you etc. You also have to demonstrate that the employer took no reasonable steps to mitigate the situation. Jazzer does have it in his favour that he walked immediately but Tom will argue that he offered alternative work on the farm. It will probably also depend what it says in his employment contract if he is employed as "Pig Herdsman" then he might have a case because it is a fundamental change. However, if he is employed as a "Farm Hand" then Tom would have a strong defence.
Jazzer might have a case around unfair dismissal for the above reasons but he would have to demonstrate that there is still a requirement for the job - difficult if there are no pigs and again he was offered an alternative.
Where he would have had a case is if he had stuck it out and Tom had screwed up the redundancy process (which, it's Tom, so let's face it highly likely) if there had been no formal consultation, notice etc that's when Jazzer could have a case. However, Jazzer may well have screwed that up by walking out.
Jazzer will be entitled to holiday pay etc and Jim may be able to negotiate a redundancy package but I fear Jazzer would lose if he went to court.
My knowledge may be a bit out of date though, a practicing employment lawyer might have a different perspective.
I also think Bridge Farm is likely to have a legal insurance package in place either through their farm insurance or the NFU. The NFU will certainly have a legal helpline. Jazzer won't have any insurance which will have legal expenses cover (unless his car insurance does but it is unlikely to cover employment)
However, someone on one side or the other will probably end up rummaging in the cereal cupboard for Usha.