Mike
It has nothing to do with whether you are receiving a disability benefit or not, it is based on whether you are receiving an Income Related benefit or a Contributary Based one.
IB is the latter as is ESA(CB) and JSA(CB), however, IS, ESA(IR) and JSA(IR) are the former.
Even if you are receiving a Contributary Based benefit, you can reduce the cost of medecines by purchasing a Prescription Pre-Payment certificate.
See
www.nhsbsa.nhs.uk/1127.aspx You may also qualify for am HC1 Low income certificate.
See
www.direct.gov.uk/en/MoneyTaxAndBenefits...rinjured/DG_10018978 Gordon