Speaking for the Peninsular War, the British Army was trained to an extremely high standard. Unlike the French, who were surrounded by enemies on all sides and so had to rapidly raise, train, and deploy troops, Britain was guarded by the Channel and the Royal Navy and so had the luxury to commit to a longer training programme for its soldiers: in the words of Richard Holmes, "it might take six months for a man to pass off the (drill) square to the sergeant major’s satisfaction." In contrast, the British line infantryman's French counterpart might receive less than three weeks training before being rushed off to war. Britain's European allies – Russia, Prussia and Austria – were beset by the same problems as France, having to rapidly raise large armies, thus producing troops of questionable quality. Britain's campaign in the Peninsula, however, was expeditionary, limited and long-term, allowing them to raise a small yet high-quality army. When it appeared that the French might gain the upper hand, the British Army would retreat to defensive positions in Portugal to regroup and rearm, as it did after Talavera in 1809 and Burgos in 1812.

Raising huge numbers of men also diluted the amount of materiel the European powers could commit to the training of each man: in weapons training, a British rifleman would receive sixty live rounds and sixty blanks; a light infantryman, fifty live rounds and sixty blanks; and a line infantryman, thirty rounds. In contrast, a Prussian jäger received sixty rounds total, while a Prussian fusilier received thirty. An Austrian line infantryman never received more than ten rounds, while a Russian infantryman would be lucky to get six. That was the genesis of the superior rate of fire and fire discipline the British Army was able to maintain in the Napoleonic Wars.

Crucially, officers also had to undergo basic training. Though purchase of commission was still in place, nearly every regiment required its new officers to do basic training, marching with ordinary soldiers, conducting weapons drill, and performing sentry duty. An account of the Battle of Fuentes de Onoro by a Private William Wheeler of the 7th Division records:

"He (Wheeler's commanding officer) took advantage of the ground and led us out of the scrape without loss. I shall never forget him, he dismounted off his horse, faced us and frequently called the time 'Right, Left' as he was accustomed to when drilling the regiment... he would now and then call out 'That fellow is out of step. Keep step and they cannot hurt us.'"

Thus, British troops were trained to the point that they could execute their drills on the battlefield as flawlessly as they would on the parade square, and the incident reflects extremely well on the level of training and drill British troops received.

EDIT: Clarification on use of blanks for those who can't read:

in weapons training, a British rifleman would receive sixty live rounds and sixty blanks; a light infantryman, fifty live rounds and sixty blanks; and a line infantryman, thirty rounds.

in weapons training, a British rifleman would receive sixty live rounds and sixty blanks

in weapons training

Sources:

Michael Glover, Wellington’s Peninsular Victories

Jan Read, War in the Peninsula

Peter Snow, To War with Wellington

Philip J Haythornthwaite, British Napoleonic Infantry Tactics 1792-1815

Richard Holmes, Redcoat: The British Soldier in the Age of Horse and Musket