Boat of Garten is about 5 minutes from the A9, the main trunk road running up the middle of Scotland. Travel times by car:
Edinburgh 2.5 hours
Edinburgh airport 2.5 hours
Glasgow 3.0 hours
Aberdeen 2.0 hours
Inverness 35 minutes
Inverness airport 40 minutes
Inverness Airport is about 40 minutes from the cottage with frequent flights from the three London airports of Heathrow, Gatwick and Luton plus direct flights from many European cities. Car rental from the major car rental companies is available at the airport.
There are direct train services from London Kings Cross to Aviemore, and if you don't want to use up the daytime travelling, you can take the overnight Caledonian Sleeper service leaving in the evening and getting in first thing in the morning ready for a full day.