I switched my Shelties over to Heartgard when they stopped producing Interceptor. I have had no issues - just remember to break it up into their food.
Sentinel is free of Ivermectin, as is TriFexis.
I personally have a problem with administering Sentinel or Trifexis, as my dogs are also ingesting the flea/tick prevention in those two products.
In my part of the country, I withhold the flea/tick prevention through the winter months. But they are on HW prevention year round - we have had too many Shelties come into rescue HW positive.
For our Collies, we order Interceptor online from Australia. Since I have not had a Collie foster in a couple of years, I don't know the websites, but maybe our friends down under can help with that?