You can now buy a generic fluconazol oral capsule instead of the branded Canesten one for much less. I went to the chemist last week for my daughter for the capsule as she said the Canesten cream wasn't helping and the pharmacist recommended the generic capsule for less than £5. I didn't know a generic one was even available.
As a preventative, if it's a chronic problem, try probiotic yoghurts like Actimel or Yakult. I had a spate of antibiotics a few years ago and I got bad thrush, but when taking the probiotics I never got it. You can also buy tablets if you don't like yoghurty things.