Since 1st April 2009, cancer patients in the UK have been entitled to an exemption on prescription charges for all medicines, not just those related to cancer. So far, though, the take up has been slow. This may be due to confusion over how to claim or a reluctance to 'accept charity' or be seen as needy.
It may be worth asking your friend or family member if they have applied for their exemption. Cancer brings with it enough additional costs, without paying for prescriptions unnecessarily.
For more information on how to claim, see MacMillan's website at http://tinyurl.com/9aw65q