I bought some Advocate flea treatment from the vet today. £48, which is a little more than I remember paying before.
However, when I got home I noticed that there were only 3 months' treatment in the box. The box was labelled correctly, but was otherwise identical to the last time I bought some, which had six months' treatment.
I see that I can obtain this stuff online for under £30 for 6 months.
Bugger!