Thanks for that John. These things are never as straightforward as you'd like!
It's a confusing lot - there was John Marshall and Elizabeth Saunders who married in 1745 and had various children, including the John who married Elizabeth Madle in 1771, so there are a lot of children of John & Elizabeth Marshalls - but I've been having difficulty finding the corresponding burials for both couples - the only burial I'm reasonably confident about is the Elizabeth Marshall buried 2 Jun 1803 at Luton aged 50, who I think must be Elizabeth Marshall formerly Madle (nee Arnold - she was married to her first husband aged about 18, but he died six weeks later). Trouble is, Chiltern Green where they lived straddles two counties and three parishes - Luton, Kimpton and King's Walden, and the Kimpton and King's Walden registers aren't properly indexed pre-1800 anywhere yet. I suspect the Ashwell Bridge lot were connnected too - Ashwell Bridge is at East Hyde, just at the bottom of the hill from Chiltern Green.
Some day I'll have to go to Luton and Hertford, transcribe all the Marshalls from Luton, Kimpton, King's Walden, Harpenden and Wheathampstead and see if the jigsaw works any better!
Thanks for your help.
Regards
Richard.