Just got back from Boots, where they are doing selected hayfever medicines on buy one, get one free.
Some of them aren't that much of a deal / a deal at all, but the only hayfever remedy that works for me (Benadryl Allergy Relief - acrivastine) is BOGOF, meaning you can get 24 tablets (2x 12 packs) for £4.39.
This is the cheapest I could find.
The 24 packs aren't included in the deal.
Online and in store.
Hope this helps someone. :)