Have you tried the Hozelock hand-sprayers - or are these the ones you're having grief with?
I find them reliable, Mr G.
Same here, Aunty!
I've had a Hozelock Killaspray since 1986, (won it in the village fete raffle here, well, I actually won a wheelbarrow but swapped it at the shop on The Moor as Peter had only just sold me a barrow a week before! And he made me pay the difference)! The nozzle does need fine tuning, and if the smallest bit of grit gets in the end, it needs a clean out!
I only use it for weedkillers now, so there's no conflict, but for the GH, these little hand-sprayers are ideal for the job, and also for the fruit trees etc.! They only cost a few quid, and are much better than Windowlene or similar sprayers!