I Think i got it!

took your advice Charles so thank you -

Master document saved as a template which contains all the AutoText i need.

All other documents then created from this template and the appropriate text added via a textField.

The auto update on open seems to have been resolved by the addition of a Marco code which changes all the fields as appropriate when opened.

all seems to work fine.

my only concern is that i didn't write the text for the marco myself and just copied it from another site offering help on the same subject, so not sure if it's the most efficiently written piece - Does this look okay?

Sub AutoOpen()
'
' AutoOpen Macro
'
With Options
.UpdateFieldsAtPrint = True
.UpdateLinksAtPrint = True
End With
ActiveDocument.Fields.Update
End Sub