Thanks John for the reply.
This from Wellington's Army: The Uniforms of the British Soldier, 1812-1815, plates by Charles Hamilton Smith, text by Philip J. Haythornthwaite (London: Greenhill Books, 2002) also further confirms the switch to bearskins post-Waterloo.

Plate 25 - Grenadiers of the Foot Guards in Full Dress, published July 1812
"It was announced in the London Gazette of 29 July 1815 that henceforth the 1st Guards would be a regiment of grenadiers, styled the First or Grenadier Regiment of Foot Guards…"
Haythornthwaite: "This honour was not appreciated universally; a member of the 1st Guards' light company recalled that:

"At Waterloo we lost our green feathers; and when I next joined the company in England, I found them with unwieldy bear-skin caps on their heads. As for myself, being remarkably short, and my cap a very high one, there was nearly as much to be seen above my face as below it; and I looked, for all the world,

Like Tommy Boddy,

All head and no body!

When we metamorphosed into a grenadier regiment, the light companies requested to be allowed to retain the feather under which they had fought so long: but this was not granted."

The account was written by 'Green Feather', evidently a nom-de-plume for Charles Parker Ellis, Lieutenant & Captain of the 2nd Battn [1st FG] at Waterloo, "Reminiscences of Bayonne," United Service Magazine, 1842, vol. II, p.85