I think that would be a good move - Clik has certainly worked well for us this year. We have seen loads of eggs, but non develope into maggots! The fact that it works out cheaper as it last 16 weeks & that we only have to treat the sheep once - sells it for me. Also, it works in a different way to Crovect. Crovect only protects the areas it is sprayed on, but Clik is absorbed through the wool & skin & moves over the whole body.
We did use Crovect pre shearing, but had a few with fly strike, so I think, although it is a very good product, the protection isn't quite as good.
I hope your sheep are doing ok now. Fly strike is a very nasty thing to deal with - for both you & the sheep.