Flight
For international guests, Aberdeen (ABZ) is the closest airport and is relatively civilised (if small!) and easy to get to from Europe, but will require a connecting flight from London (Heathrow/Gatwick/Luton etc. You may, if you wish, catch a train from central London for the whole European train experience thing. It is longer in duration than a flight (from 8-13 hrs depending on many variables, sometimes faster to drive!), and is also a bit more hassle getting through to the train station in central London - but if you book first class and have scheduled/locked seats, can be a nice relaxing experience - with good views during the day time. It *is* slower (even with airplane check in times these days) but is cheaper (if you book *well* in advance). Trains in the UK are notorious for delays or can have issues - Europe this is not ;)
Travel Note
It is possible to get an Uber from Aberdeen to Glentanar, however, Uber is not yet present throughout Scotland, so it is recommended to rent a car (several companies at Aberdeen airport or the city center) or a traditional Taxi service (taxi ranks at Airport, or train stations/bus terminals). For those requiring there are many high end Chauffeur travel taxi firms, reach out for more details if interested. Aside from Uber, Lyft and other international modern Taxi apps are not yet available. If you plan to stay longer or require more flexibility touring around, a car rental would be cheaper and much more flexible. Please note, there are few automatic transmission vehicles in the UK, most rentals are manual/stick shift. Book far in advance to lock down an automatic transmission vehicle and be prepared for a possible surcharge (sometimes depending on the car rental company).