I think we must all be wary of dishing out advice which suits our own area and could be interpreted as being generally applicable.
Hereabouts, in Cumbria, there is currently no time of year when we do not need to treat for fluke. We had active fluke in lambs in August last year - it was so wet and cold all year, they never took a break.
There are a lot of reports of triclabendazole, the flukicide in Fasinex and in Combinex, becoming ineffective. Certainly we have had batches of ewes we have needed to treat with other flukicides in order to get them healthy. It could be that it's been such an extraordinary year and the fluke have gained ground, or it could be that there is some resistance developing.
The flukicide in Closamectin for Sheep is closantel, which is also in Flukiver, Mebadown and Superverm.
Combinex
looks white but the wormer in Combinex is Levamisole, which is a yellow drench.
Download yourself a copy of the BRP Parasite Control Guide; the reference tables at the back are bloomin' priceless!

Get yourself some of the Eblex Better Returns Programme (BRP) guides.
Download them here
Read "Manual 8 - Target Worm Control..." first, then the "Booklet - Parasite Control Guide" which gives you a lookup table of which meds has which active ingredient.