In "The Chaos of Empire: The British Raj and the Conquest of India" by Jon Wilson, the topic of what became of the British soldiers and civil servants after Independence in India and Pakistan is touched upon in chapter 15, the Great Delusion.

'Officers returning home could take up pensionable opportunities in 'another civil service' with a grant of 500 British Pounds. Or they were given a 'severance allowance' equivalent to full pay to the usual retirement age of sixty with the prospect of a good pension afterwards.

'Old Indians' who did not take other jobs could maintain the same living standards as dentists and doctors without having to work, but the vast majority put their experience in the machinery of administration to work.'

The collapse of the British Raj roughly coincided with a rise in wages and living standards in the United Kingdom. The economic boom lasted well into the 1960's. Britain in 1947 was still rebuilding from the German air raids and rocket attacks of WWII. Tradesmen made a good living, labor union membership was up, and British manufacturing was on the rise. The author gives the UK a 24.6% share in the worlds manufacturing exports in 1950 to the United States's 26.6% share. So even the 28,000 some British conscripts serving in the British Army in India at the time of independence went home to a prosperous nation with many employment opportunities and much work to be done.

For many British in India, there was no point in staying on after the evaporation of British sovereignty. They'd led a somewhat paranoid and precarious existence in India. Secluded away in cantonments, British soldiers and civil servants formed few relationships with the local communities of Indians around them. Throughout their occupation of the sub continent, they preferred to attack or withdraw behind their fortifications when confronted with a problem rather than negotiate with the people of India. When the separation was formalized, there was little for them there.

That's not to say that all of them left. A few with specialty skills in the revenue departments (tax assessors, customs officials, etc.) were offered generous salaries to stay on for a time, by both Pakistan and India. Their knowledge and expertise was needed, as the new nations had a need to measure the productive capacity of their domains and citizenry. These specialists were in a good position to provide valuable insight to the new regime. The last British Civil Service man to depart was J.W. Orr, an Inspector for Customs and Excise in Delhi, who retired in 1955. Most of the soldiers left within a year of Independence.