I meant to post this earlier. It's not comprehenive, but it helps build up a picture. I'll cross posting to the barbering thread.
1823 Orders for 9th, 12th 16th and 17th Light Dragoons to convert to Lancers
Moustaches to be grown
1830 The whole of the cavalry with the exception of the Royal Horse Guards (Blue) to be dressed in red at the next issue of clothing. / The mustachios of the cavalry (excepting in the Life Guards, The Royal Horse Guards, and the Hussars,) to be abolished, and the hair of the non-commisioned officer and soldier thtough out the regular forces, to be cut close at the sides and at the back of the head, instead of being worn in that bushy and unbecoming fashion adopted by some regiments Circular, Horse Guards, August 2nd, 1830
General Lord Hill [C-in-C]
1832 Moustaches. Mr Editor- I fully concur in the opinion … that the moustache added considerably to the soldier-like appearance of our cavalry, but mark the absurd inconsistency which has attended their abolishment. The moustache was ordered to be abolished in consequence of his Majesty’s dislike to everything not perfectly British, and yet to strange to say, the only regiments allowed to retain the ornament, are HIS MAJESTY’S OWN HOUSEHOLD TROOPS, and the Hussars, to the dress of which latter corps… the moustache belongs, and why? Because hussars are altogether foreign… United Services Journal March 7th 1832
1st May The General [C-in-C] has, again, been desired by the King to call the attention of General Officers, and Commanding officers of Regiments, to the repeated orders that have been issued by Her Majesty’s Commands against wearing long hair and whiskers- Circular- Memorandum
‘Received 10th May’
21 July “a Circular Memo bearing date 21 July 1854 was promulgated announcing that moustaches were authorized to be worn". [Sergeant] Charles Usherwood's Service Journal, 1852 – 1856, (Diary of Services in the Crimea by Charles W Usherwood and while serving with the 1st Battalion 19th Regiment of Foot
1862 ON the 18th the 71st were paraded for inspection, at the conclusion of which Sir Hugh Rose made them a highly complimentary speech, telling them, in allusion to the fact of the men being clean shaved, that he was glad to see that they kept up the old custom of the Regiment by not wearing either beard or whiskers, which was an old characteristic of the corps
HLI Chronicle October 1912 (p.293)
'FIFTY YEARS AGO'
(Extract from the Army and Navy Gazette February 8, 1862)
1868 358. The following directions in regard to the growth of hair are to be strictly observed by all ranks. The hair is to be neatly cut, and kept short. Moustaches are to be worn, and the chin is to be shaved (except by pioneers, who will wear beards also). Whiskers, when worn, are to be of moderate length. On active service in the field beards may, however, be worn at the discretion of the General Officer commanding.