It has Tilbury there too Paul. Oxford Dictionary of Place Names has Tilaburg 731, Tiliberia 1086 (Domesday Book). Derivation stronhold of a man called Tila (though Tila could be a the name of a lost stream. Tila = the useful one).

The use of Tilsburie would accord with a genitive s Tilsburie = *Tila's burie equivalent to Tila-burg. A quick search for Tilsburie seems to find it always in the context of the title given above by Chico. See for example the article on Deloney: Deloney or Deloney - Misc Ballads, Notes. In the days before orthography was so regulated perhaps that's just how he thought it should be spelled!

Mick