Are you aware that the Gloucestershire Record Office has some useful online tools?
1) Summary catalogue of (some of?) their collections. A search on 'Ashmead' reveals that they have the deeds of Ashmead Farm 1620-1794.
2) Index of wills (and some other bits and pieces) This has 85 pre-1800 Ashmead wills, and gives locations. I've looked at some of the later ones, helping the other researcher with his links to Bristol, but haven't looked at any of the earlier ones yet.