No such definitive list exists as far as I know.
The ANO Article 74(1) says 'A person must not act as a member of the flight crew of an aircraft registered in the United Kingdom if they know or suspect their physical or mental condition renders them temporarily or permanently unfit to perform such functions or to act in such capacity.
I believe that the reason that there is no list is that each medication can affect everybody differently and so a list would inevitably miss a drug that has an adverse effect on someone. So the law puts the onus on the individual to assess themselves. That said, the CAA has a list of drugs (a good many of which are available over the counter) that are deemed to render a licence holder unfit to exercise the privilidges of the licence for some reason, irrespective of how he or she might feel. But I don't think the CAA's list is published officially anywhere.