That is an interesting idea, and 'Elizabeth' could well be Betty. I hope you received my message yesterday, saying that the two signatures of Timothy are indeed comparable and I fully accept that Betty Chappelin was his wife. The Trenizon name came from the lot description in the Christies catalogue for the sale of Richard's portrait, which I imagine came from the family, who might also have provided the date of 1742 for Richard's birth. I found on Ancestry Marjorie Baylay who posted a number of photos, but the contact may well be too old. I will ask Wiltshire and Swindon History Centre whether they have any further information.
Warm thanks again
lambre