If you can, collect supporting information from other agencies, school/colleges, GP, nurse and hospital consultant or learning manager if appropriate - the more info you can collect that supports his needs and yours!, the better!
Next, write to the department manager, always state you appreciate the workers comments (no ned to overly antagonise...yet!) but need to arrange a meeting with the manager for further discussion and possible reveiw of all the relevant info.
Seek out your local councillor - there's always a councillor with a social services remit but you need to contact them through your own one and he'll know exactly who to contact on your behalf!
Be prepare to fight your corner, the better your supporting evidence the easier the fight will be. Be prepared to appeal to a higher level and lastly get everything and I mean EVERYTHING! in writing (emails are usually quick and easily printed off when needed!).