Hi 1048claire
The DWP member of staff told your son correctly, If your son is in receipt of UC and LCWRA then he will not be able to claim the Carers Element, £163.73 pcm. UC regs, regs 29 - 30
Your son could claim Carers Allowance but it is a taxable income and would affect his UC claim.
I would advise you both to seek advice from a Welfare Rights Organisation, depending on your circumstances both you and your son may be better off if he did not claim CA for looking after you. You can find your local Welfare Rights Organisation to help you with advice by clicking on the link below and putting in your post code, it will then come up with a MAP with a list of agencies.
advicelocal.uk Gary