Found - the first documented link between the "posh" Armstrongs of Ampthill and Houghton Conquest and our branch:
http://tinyurl.com/26xcm8The John Armstrong at the beginning of the references is son and heir of Charles, who was son of Thomas and Frances Thompson. Thomas was allegedly born in Ireland and settled in Ampthill on his retirement from the Army in 1717. He was a JP - references all over the place on BLARS. His wife Frances was daughter of Lord Haversham and granddaughter of the Earl of Anglesey.
John Armstrong must have been at least 21 to be entering into leases, so born before 1767. This puts him in the right age-group to be a son of Charles - but I cannot find a John born to Charles. Charles' children with Althamia Priaulx were born between 1749-1752 in Steppingly. The Ancestry trees say he had a first wife named Elizabeth, with whom he had one son, Thomas, but I can't find him either!
The key item is right at the end - John Armstrong's will. However, this can't be the John mentioned in the first line - he must be the next generation. He is definitely from that family - the Althamiah pegs him firmly to the "posh" lot:
"Recites (9) - will of John Armstrong 7 June 1841
- To daughters Mary Ann Armstrong and Althamiah Armstrong 400 each on attaining 21 years, and if one should die her share to go to the other, if both should die the legacies should lapse for the benefit of the owner of the estates,
- To friends Charles Armstrong, farmer, of Wootton and
William Armstrong, farmer, of Hawnes, his personal estate and messuages, tenements and lands, on trust to provide from them 52 a year to wife Mary Armstrong, with power of sale.
Executors: Charles, William and Mary Armstrong as above, will pro 19 June 1843 at Bedford."
I have found his death on FreeBMD, qe Jun 1843, and two daughters on the IGI baptised in 1827 and 1830 respectively. There seems likely to have been a son John in 1832 and a Sarah Augusta in 1835 as well. Though with everything left in trust for his wife and daughters, there couldn't have been a son surviving by 1841, but I can't find a likely burial. Sarah Augusta died qe Sept 1838.
It's interesting because it is the first visible contact between the Ampthill family and ours.