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☼ Linser, Pte George (or Thomas), (1589), 4th LD (p 54)[Dutton 52]
Bn in Brixton [of Brides][54-4-20], Devon. Enl 02-01-54 in London at age 20 [54-1-7]. Prior Occ: Groom [54-4-20]. Rode in Charge;  wounded & taken prisoner [54-4-5, 20][CR 38]. Father, John Linser, Surrey Co., Wimbledon Parish [54-4-20]. Medal [202] w/ A [202], B [228], & S [224] Clasps. FN listed as “Thomas” [CR 38].

☼ Dewdney, Pte Walter, (1211), 17th L
Enl 04-05-54 [54D-2-5, 20a]. In Hosp 2nd & 3rd Mstrs [54D-3-5]. Prom 10-01-54 to Cpl [54D-4-4, 5]. Prom 07-01-55 to Sgt [55D-3-3, 4]. To Svc Trps 11-01-55 fr Brighton Depot [55D-4-3]. Joined Regt 11-21-55 [55-4-3]. AA Charge. Not on MRs though served in Crimea.

As you can see, Walter joined the military early in 1854, and had risen to the rank of Sergeant by July 1855; he was sent to the Crimea, but arrived after the fall of Sebastopol, and therefore was not entitled to a Medal or any clasps.

Don't know if this helps any, but it is worth a try:

From my book:
☼ Kilvert, Cpl John Ashley, (1513), 11th H (p 142)[Dutton 170]
Bn 09-29-33 in High Ercall, near Shrewsbury. At  sea 2nd  Mstr; at Varna 3rd  Mstr [54-2-5]. Prom 07-09-54 to Cpl vice Guttridge [prom][54-3-4, 5]. Rode in Charge [BCS 1879];  wounded [CR 36] by a musket ball through his right leg;  the ball subsequently wounded his horse but the horse continued to charge.  On meeting the enemy Kilvert sustained a slight saber cut to his head.  On returning to the allied lines, his horse had to be destroyed immediately.  Kilvert was lain in a ditch to wait for an empty ambulance & he was discovered there by an ambulance party after dark nearly frozen to death. Prom 10-26-54 to Sgt vice Jones [killed][54-4-3, 4]. Wounded /  at Scut 2nd  Mstr & in  Hosp at Scut 3rd  Mstr [54-4-3]. Inv fr Scut to England 1st Mstr [55-1-3]. Recruiting at Bath all 3 Mstrs [55D-3-3] thru [56D-1-3]. Medal [390/397] w/ A [390/397], B [406], & S [413] Clasps. Member BCS 1877 & 1879 [GM 39]. Signed Loyal Address of 1887. Att Ann. Dinners in 1892, 1893, 1895, 1899, 1906 & 1910. The only members of the Light Brigade outliving Kilvert were W. H. Pennington & Edwin Hughes. Died 10-17-20 in Wednesbury, Staffordshire. Buried 10-22-1920 in Wood Green Cemetery, West Bromwich, Staffordshire. His sword & medals were bequeathed to the Wednesbury Art Gallery. Kilvert was the model for the wounded soldier depicted on the dust cover of Honour the Light Brigade [KH].
Dutton mentions the 1881 census has him living at No. 1 Hitchen Croft, working as a pawnbroker and running "Croft Pawn Brokers". He was living with his wife and son and an employee. His wife at the time was 48 years of age and born in Wednesbury, Stafford. His son was born in Coventry.

Dear Linda:

Retirement was much an individual matter; initial enlistments for the cavalry were for 12 years, and many of the men re-enlisted at the end of that time. Conditions of army life (housing, workload, diet) wore men out before their time, so that some relatively young men (late 30s to early 40's or even younger) were 'discharged as useless' based on their inability to fulfill the necessary duties. Men were also allowed to purchase a discharge if they wanted out of the army before the end of their service commitment.

As the movements of the Lancers are not a particular specialty of mine, I had to cheat and look it up, but they do not appear to have spent much time in Ireland around the time of the war. If you want to check out more specifics, go to "Google Book Search", do an "advanced book search", use "17th Lancers" as your search term and do your search for a "full view only." Two of the most authoritative books on the history of the 17th Lancers are available there to download in their entirety as PDF files: Fortescue's "A History of the 17th Lancers" and Parry's "The Death or Glory Boys."
Farrier-Major or Farrier-Sergeant was the NCO in charge of the farriers that tended to the horses to include blacksmith duties.

No Patrick Caughlin/Coughlin served in the Light Brigade (which includes the 4th Light Dragoons) during the Crimean War . . . nor could I find his name listed with any of the regiments of the Heavy Brigade.