Hi Matt
I’ve done a fair bit of looking into the Smithson family too. The wife of one William Smithson that died in 1625 - Rose, went on to marry a George Epps in Shadoxhurst 1628.
But, I’m afraid I’ve probably wasted both of our times
Margaret Smithson dau of William Jnr. buried 21 ? 1618 Shadoxhurst.
Other Margaret’s I’ve just spotted
Margaret dau of John Smythson baptised 12 Sept 1612 in Wye.
And I’m not positive there looks to be one in Sandwich but I think that’s possibly too far away.
John Smithson of Wye - two possible marriages both in Wye
J Smithson and Bennet Jones a widow married 11 Sept 1598
J Smithson and Margaret Note married 20 April 1601 - this looks good 
Claire
Hi Claire
Well that explains why the Margaret who was christened in 1618 isn't mentioned in the 1625 Will of William Smithson [junior]. Good to know I wasn't going mad lol!
It wasn't a waste of time though, after all at least we can eliminate Shadoxhurst from any enquiries.
Wye is about 6 miles from Charing so a little closer than Shadoxhurst anyhow. I'll look into the Smithsons in Wye and see what else I can dig up.
I've got another puzzle which I'd like your opinion on regarding my Chambers family but I will email you about that later.
In the meantime I'll let you know what I can dig up about the Smithsons in Wye.
Matt