Sorry to hear of this, imd123. I recall your earlier posting, and your son really has come up against the nastier realities of work in 21st century Britain.
The earlier advice you got from Buenchico and Themas remains valid. I don't think your son has much chance of recovering from his former employer.
But you do not mention following up advice to contact ACAS, who should definitely be able to help. You can get contact details of the nearest office from the internet. They can also tell you about the government's Insolvency Fund, now run by the DTI. This agency will not advise you, but will pay out for work done but not paid for (the bounced cheque), for pay in lieu of statutory notice and for any statutory redundancy pay that would have been due; it then tries to recover the money from the employer, but that is not your problem.
Where I am less certain is whether those payments would be made at the actual hourly rate or the relevant (to your son's age) national minimum wage rate. Logically it should be the latter, but I am not sure.
Good luck, and try to make sure that your son's next job is in a union-organised job.