If making people redundany you have to consult with them. I am the manager of a small company currently making people redundant so I do know about this.
If you are making 20 or more people redundant you have to consult for a month. If less there is no minimum consultation period, but even if only 1 employee to be made redundant they have to consult. However, could in theory take 1 or 2 days only if less than 20.
They have to consult on the selection procedure for choosing who they will make redundant, anything they can do to avoid compulsory redundancies e.g. ask for voluntary redundancies; and what they can do to make the affects of compulsory redundancies lees bad (called mitigating against affects of redundancies) e.g. offering access to training.
Even if they consult through a union, they still have to consult employees directly.
Statutory redundancy pay only becomes applicable after working somewhere for two years. It is 1 weeks pay for every year you have worked up till a maximum amount (about £400, can't remember exactly as it has just been increased) or one and a half weeks pay for every year if you are aged over 40.
All staff should receive pay in lieu of notice (need to look at contract for notice period) and pay for any holidays due but not taken.
If someone is made redundant they must be told in writing why they are being made redundant (but this can be because of lack of income);how much redundancy pay they will receive and how this has been calculated.
In terms of your situation, I can't imagine they will give anything if he volunteers for redundancy. But they are definetly not following proper processes.
If any workmates are in a union can your OH contact them this weekend and ask them to contact the union, as they are not following legal procedures. You could also contact your regional ACAS office for advice and see if they will intervene. I think they would intervene in this situation but not 100% sure. Should be able to get contact through google.
ACAS will work with any size of firm and their role is to stop claims getting to industrial tribunals - usually through negotiation. But I think they would ring your OH firm and advise them that they are not following legal procedures and what they need to do.