la Chausee 19.1.1800 at Lanesborough's
Major La Chausee, le comte de la Chaussee "Memoire militaire sur Bantry" 26.4.1797 (Kent History Centre / photopol.com/articles/bm_corr.html). La Chaussee had to show Thomas Pelham 2nd Earl of Chichester how to load a mortar 13.8.1797. Not in British Army Lists. Probably Charles de la Chaussee, Seigneur de St Aubin (Dictionnaire de la Noblesse Francaise)
La Chaussée
A colleague directed me to your entry on La Chaussée. The link you have via Kent is to a page on my site. It may need some slight updating which I hope to get round to. I think the La Chaussée in question is actually the son of the man who was Seigneur de St. Aubin. The father was born in 1705 so he would have been a bit old to be traipsing round Ireland, London and Jersey in his nineties. The son (b. 1753) fits the bill and was suggested to me as the most likely candidate by the Bibliothèque Nationale de France as far back as the 1970s. I thought there were some anomalies in his dates for a fit but on boning up on my French history I think he fits well enough.
Regards.