Some quibbles about the British Army:

The British Army as a whole has belonged to Parliament (not the Crown) since Cromwell's time, and is never referred to as Royal. Many regiments and corps have royal sponsors (e.g., the Royal Corps of Transport) but not all (the Army Catering Corps).

In its troop-levying practices, the British Parliament has racked up several centuries of -- shall we say -- equal-opportunity oppression. Mercenary regiments came from Scotland (e.g., Fraser's Highlanders) and Switzerland (Haldimand's Legion) as well as Hesse and Hanover by the same mechanism: colonels were invited to raise regiments at War Office expense, which were then simply added to expeditionary forces by royal order through the War Office. Britain used mercenaries in this way as late as 1857, when Hessian troops were hired for operations in the Crimea.

Because of Europe's international alliances and royal dynasties, 18th-century European armies were truly multicultural, while each being a subculture of its own. The British Army absorbed its non-English elements through its regimental system, maintaining the outward and visible signs of difference such as kilts, grenadiers' caps and bagpipes, and imposing army-wide culture throughout the ranks by means of discipline, training and long stints of overseas service.

During the Imperial period (1860-1945) Indian, Ghurka and African regiments were raised by the same methods, but generally employed for the defence of British interests in their own regions -- except when the War Office needed trained soldiers elsewhere, such as South Africa (1899-1902) and France (1914-1918). That said, in the Imperial structure of the 19th century, coloured [sic] regiments never received the considerations and dignity (such as they were) extended to white regiments.