I would definitely second the vote for buying online, and it's cheaper too.
Never ever just go for Canestan as it is way more expensive than the generic equivalent.
And I guess that using the fluconazole tablet is less likely to irritate your bits than using cream directly. It obviously doesn't target the area, so as CLKD says, eat lots of decent live yogurt too.
Oh, and if you do get age-checked at the chemist, just tell them yes, I am that old, and I think my thrush is due to the rampant sex that I obstinately continue to have, so there!!