Tescos had their own version out last year I think, my dads wife gave me some and they were excellent. (I usually just use a sniffy thing and some eye drops but my hayfever is worse in London that it ever was in Guildford).
check out all the supermarket own brand hayfever stuff, you can save yourself a fortune. asda smart price are near enough the same as benadryl and a fraction of the price. i speak from experience, they work.