Thomas
Not sure of the travel times exactly but Boat of Garten to Brora is likely to be a couple of hours ? Likewise Silloth to Southerness, even with the new bypass round Carlisle, that's a couple of hours. Better combo's in that they don't involve as much travel would be;
Silloth & Carlisle or Seascale
Southerness & Powfoot
Boat of Garten & Granton-on-Spey/Kingussie/Spey Valley (any of the 3) with the nine holer at Nethy Bridge thrown in.
Niall