I suggest Laxenburg, obviously, It was the refuge for the last emperor , Charles (Kaiser Karl) after WW1 , his abdication and under the protection of a British officer charged with that task.
Sorry, but a little historical correction. The last Austrian emperor, Charles I., used Laxenburg as a residence in 1917/18. After Austria's surrender ending WWI Charles signed the so called "declaration of waiver" saying that he will refrain from any action in governing Austria. This was a de facto abdication although he never used this term and felt being still emperor until his death. (Same for his wife Zita who was not allowed to enter Austria for about 80 years because of this.)
After having stepped down from the throne Charles, his family and his entourage of about 100 people had to move into the much smaller Eckartsau palace which remained private property of the Habsburgs, while all other palaces were expropriated and taken over by the young Austrian republic. Charles' attempts to re-install the monarchy failed. Living in Eckartsau was dire because of both the famine and the Spanish flu.
At the end of February 1919, a British Army officer arrived at Eckartsau: Colonel Edward Lisle Strutt delivered a letter of solidarity from King George V. of England to the Austrian ex-monarch, assuring Charles of the British government's "moral support." Strutt also brought a shipment of urgently needed food and medicine.
When Switzerland finally expressed its willingness to grant Charles and his family asylum, Colonel Strutt organized their departure by train.