Here is the pedigree for the latter Greys. (from my water damaged copy - it was in a fire and hosed down by the fire brigade in the USA - I kid you not)
I see Sir John Grey had a brother killed at the siege of New Orleans, 1815.
So the estate passed to cousin Sir George Grey of Fallodon. But Madame Maria Senillart of Boulogne got a 100 quid annuity?
Services rendered during the Penninsula War perhaps
I wonder if Capt Tate connects to the Greys via marriage?