DH was offered part time work for a company but only as a self-employed contractor and not as an employee (on the books). He accepted the offer (as was recently made redundant) and worked for said company for 3 months, submitting an invoice at the end of each month for monies owed. At the end of the 3 months he still hadn't been paid so decided not to continue working for the company but regularly phoned the Office Manager to see when payment may be received. We are now nearly 3 months on and still no payment. He has sent a letter to the Accounts Manager and Office Manager (recorded delivery) but still no payment. We understand that the money owing is not very much but now its a matter of principle
. Is there anything else we can do? any help is much appreciated 
I must add, this is a company he knows very well as has worked for them on a permanent basis in the past.