Raggy take a look at the following:

"The number of states headed by Queen Elizabeth II has varied during her 65 years on the throne, altogether seeing her as sovereign of a total of 32 independent countries during this period. In her capacity as Queen of the United Kingdom (including the British overseas territories), she is also monarch of three Crown dependencies—Guernsey, Jersey, and Man—and, in her capacity as Queen of New Zealand, she is monarch of two associated states—the Cook Islands and Niue—since they acquired this status in 1965 and 1974, respectively.

Two countries are unique: The government of the unrecognised state of Rhodesia proclaimed its allegiance to Elizabeth II as queen of Rhodesia from 1965 to 1970. However, she did not accept either the role or the title and it was not accepted or recognised by any other state. Fiji became a republic through a military coup in 1987, after which its Great Council of Chiefs continued to recognise Elizabeth II as queen, or Paramount Chief of Fiji, until the council's de-establishment on 14 March 2012. However, this was only a ceremonial title, with no role in government at all."

Now that would mean that anyone from any of the above could swear an oath of allegiance to HM Queen Elizabeth II as their Head of State without any problem.

As far as Nepal goes, the country through long standing treaties and agreements with the UK, India and Brunei. The connection with the British goes back to 1815 and any Gurkha who serves a minimum of fours years in the British Army earns the right to settle in the UK.