We saw the signs on one last weekend so rounded them all up.  In fact the ewe in question had a cut which was attracting fly attention but the Clik was doing its job and preventing an actual strike.  We haven't had a bad summer for flies but they're all over the place at the moment, so pretty pleased with Clik.  Still keep a supply of Crovect in case though.
We took the opportunity to crutch them ready for the ram, manicure their nails etc.  I mentioned this to a colleague without being too descriptive.  He looked puzzled so I likened it to to a Brazilian and he nearly choked...