have looked at your other thread too.
Firstly he definately cannot go on strike by himself. If he did it is one of the few areas of legislation where dismissal is considered to be automatically fair (whatever the reasoning behind the 'strike') and he cannot take any grievance to a tribunal, for example.
Secondly as he has been employed for less than a year he has very minimal rights anyway. The firm cannot (as they have done) 'make him' go self employed, but they are perfectly able to fire him for any non-discriminatory reason they choose (discrimantion, or whistle-blowing, has more protection but I doubt this will apply). They would have to pay his notice period but that would be it. So he is not in a strong position here.
Thirdly, as was pointed out on the other thread, you can't just say someone is self employed and then make it so. So it is all a bit of a mess anyway (but you know that). I suspect knowing that won't help though and his bosses will just shrug and say 'take it or leave it'
Fourthly, the company appear to be dodging tax and now dodging paying your husband. Just because you don't have a contract doesn't necessarily mean that you can't rely on what was verbally agreed: If you can show that both sides acted in accordance with your expectations as to the content/nature of the work (eg they gave him jobs, he did them), then your DH has acted 'within the terms of the contract' even if those terms are not written down anywhere. Teh problem however is that they will probably just say 'so sue us' and that is what you will need to do. You will probably need to get specialist legal advice on all of this, and that might cost a huge amount of money. My gut feeling is that this is possibly a scam and they may stitch up people in this way all the time, which means you might never see the money. It might be an idea to contact the Local Trading Standards officers wherever this place is based to see if there are black marks against this company (but I confess I don;t know if Trading Standards keep details of employee issues as well as customer issues, perhaps not). Can you also get hold of the Company Registration number of the firm? Try here as a starting point. Then take the company name info, call the IR and say you are concerned as to whether the company has been paying Ni/Tax contributions, can they please check (you will need NI numbers) - when they say 'no' (as they will) ask them for guidance on what to do and explain position to them. They will be most helpful . Especially if your DH has a list of other drivers as well .
Fifthly (?), I don't think you will get to this stage, because of all of the above, but in the long term there are some benefits from going along with being self employed in tax terms (esp if you form a ltd company), but it can be a mess of form-filling and so on and you need good advice from an employment-specialist accountant.
If you were to be particularly machiavellian about this, your DH could shop them to the IR as per point 4, then go and tell the bosses that he has reported them for not paying his tax/NI (telling them that they have a legal obligation to pay his tax, because he has a verbal employment contract, and is an employee per UK legislative definitions. At which point they will fire him (or thump him. Same difference). Then he can go to a tribunal and claim that he was fired for 'whistle-blowing' and was hence unfairly dismissed. He could then go to a tribunal (because with whistle-blowing you are still protected even if you have worked for