The best hay fever med (also not very well known- so I mention it here) is cromolyn nasal spray. It keeps your nose from releasing histamines in the first place (a "mast cell stabilizer"), reducing/removing the need for antihistamines.

Saves my springtimes: without it I'd huddle indoors wrapped in filters for 1/4 of the year. With it I can withstand all but the pollen-fog days: then I also need antihistamines.

It isn't a steroid (like most other sprays I've seen in the US or Canada) so no limits on how long to take it. Nor is there a rebound when you stop. Instead it builds up and fades away slowly. (still mostly effective after the first spray, but takes a day or two to be fully effective.)

Don't know about availability in the UK. In the US/Canada it is over the counter (has been for 10 years). Other names for it (from medline) Cromolyn Nasal Solution, Gen-Cromoglycate, or sodium cromoglycate. In Canada I've seen an eyedrop version.

Hope you find some-- I want you relaxed and back to writing as soon as possible.