Yeovil had a Penny Post; the following are examples of some of the receiving house handstamps starting with "No.1" which was Montacute.
Receiving House "No.2" was Stoke.
While Receiving House "No.4" was Haselbury.
And finally a cover from 1945 that I believe is associated with Yeovil - the US 159th General Hospital was at Yeovil and this letter has been sent free from there in the US Army Postal Service.