I was curious if they received a hero’s welcome or were they treated poorly like soldiers returning from Vietnam. Additionally, were there any British defections at the end of the American Revolution? Would the Americans have been open to a British soldier defecting and making a life in the colonies?
Generally, soldiers had never been well received by the British populace from the seventeenth century and onward. The British people characterized the common rank and file soldiers as troublesome and of the lowest classes, other common folk thought the same towards soldiers. Before the professionalization of the British army in the middle of the seventeenth century with Oliver Cromwell's New Model Army, armies usually comprised of temporary soldiers much akin to militias or reserves. These temporary soldiers would go back to their homes lacking a job and cause trouble for their fellow townsmen. These ideas did carry over in the eighteenth century with common depiction of soldiers coming from the "scum of society."
There are some sources that do show that the British people or newspapers had some sympathy for the Americans, but this did not mean a full support of the Revolution. Horace Walpole, who greatly expressed sympathy and kinship during the war with the Americans, supported the rebellion. Other Whigs of the time did as well such as Edmund Burke. The British knew that if the kingdom lost these colonies, they'd not only lose economically but geo-politically as well. They would look weak in compared to their enemies having lost to a fledgling nation born out of former colonies. Trade also had suffered during the war as Britain relied on the American ports for commerce and exchange of goods/material.
The treatment of returning soldiers varied as some experienced a return to their previous life with no ill-will while some faced hardships of no employment and mistreatment. A Rev. James Woodforde took pity on a soldier and gave him a shilling and six pence - enough to live on for about a week in those days. Most soldiers that returned home would be discharged or out-pensioners of the Royal Chelsea Hospital. Regiments that did not disband either took up garrison duty or began their travels for a new campaign. Even some of the officers felt some struggle returning to civilian life, and often found another regiment to continue their military career instead of returning to home life. Highlanders probably got the best reception home all around. By the mid-eighteenth century, the Highland economy relied somewhat on militarism, but some landowners still needed a labor force to run efficiently. The demobilization of soldiers gave them the chance to get laborers back on the lands - something not most landowners in England or Lowlands of Scotland needed.
Slyvia Frey 'British Soldier in America'
Peter Way "The scum of every county, the refuse of mankind"
Matthew Dziennik 'The Fatal Land'