Lel,
Here are some possible marriages - he could have married elsewhere other than West Firle, but it's difficult to know how far afield to look. I tried to stick to only Mary or Ann as the wife but included others where the parish was close by.
Thomas Weller m Frances Hide
23 Apr 1684, West Firle, East Sussex
Thomas Weller of Chailey m Mary Savage otp by licence
27 Apr 1708 Newick
Thomas Wellar m Ann Rothwell
9 May 1711 Ringmer
Thomas Weller m Ann Taylor
19 Oct 1740 Glynde
Thomas Weller & Ann Pierce minor both otp by licence
9 Sep 1764 Beddingham
(licence gives his age as 22 and husbandman of Beddingham)
Thomas Weller & Ann Mockett both otp
15 Apr 1782 West Firle
Thomas Weller (labr) m Lydia Hyde wid both otp by banns
17 Nov 1784 Beddingham
Alexander Weller m Susanna Gladman both otp by banns
11 Feb 1804 West Firle
Second marriage for Alexander
Alexander Weller widr m Mary Mockett both otp by banns
24 Apr 1808 West Firle
Alexander Weller bach m Katherine Mockett sp both otp by banns
23 Dec 1820 Brighton
Alexander Mockett Weller otp m Ann Elizabeth Merrell
18 Dec 1834 Maresfield
There are lots of posibilities for William Weller.
Let me know if any of these help or you need more.
Nell