The UK Ordnance Survey makes available free mapping resources for use in projects under their OS OpenData licence http://www.ordnancesurvey.co.uk/docs/licences/os-opendata-licence.pdf
One of these sets of data that may be useful to people with British Ancestry is the parish boundary maps. FTAnalyzer can use this data and it is provided here under this licence. Please note this data Contains Ordnance Survey data © Crown copyright and database right 2013-2020
The data set is current parish boundaries and won’t match exactly with historic parish boundaries as these do occasionally change. However for the most part the parish boundaries have remains as is for hundreds of years.
To install simply unzip to any directory eg: c:\Custom Maps and then in Tools, Options, Mapping Settings in FTAnalyzer set the custom maps folder to this directory. You also need to tick the box to Display British Parish Boundaries.