Firstly, glad to hear you're in remission Paul - onwards and upwards!!
My other half has spent the winter in Arillas and consequently had to take three months worth of medication ( - and he's on TEN different types a day), which as you can imagine, was a considerable amount. He had similar concerns to yourself, and rang the surgery, told them the situation, and his GP emailed him a letter to take with him, confirming his medical requirements. In the end, he put the majority in hold luggage, and an 'emergency' supply in his hand luggage and it wasn't a problem, he didn't wasn't questioned about it at all, but he may have just been lucky.
I'd just like to point out, that simply by being in Arillas, his health has improved enormously. Yet another reason for going ( - as if anybody need one!!)