Thanks - and I've just found
these posts on an Ancestry forum which seem to confirm that while the GEDCOM file format can handle this in theory, it isn't supported in practice.
Sources (but not any media attached to them) and media attached to a person will import OK into Family Historian and Roots Magic via a Gedcom Export in ANSI format from FTM, albeit they initially show with the path of the file as the media title. The media itself remains in the FTM folder and isn't moved into the Family Historian or Roots Magic media folder.
FTM doesn't appear to allow for media attached to sources to have a link exported to Gedcom. As most trees sync'd to Ancestry will have the media for an Event/Fact attached to the source record for that Fact/Event (as that is what ancestry does), this means that the link to the media won't export to any other software package. Whether that is just to do with Gedcom standards or whether its to do with FTM I don't know.
A possible long winded workaround is to go through a tree and manually attach such media to the individual as well. This is the same as when someone saves an ancestry record to their ancestry tree and then uploads a separate copy to the media section for the same person.
This is the same when exporting via Gedcom from FTM to Roots Magic. There has been a little misinformation on the ancestry Message Boards regarding exporting FTM trees to Roots Magic natively (ie not via a gedcom). If FTM is version 2006 or earlier, then a full import is possible. From version 2008 onwards, a gedcom has to be exported for import into RM. RM's own website does specifically state this but mentions V16 of FTM which was known in the UK as 2006 (and may have been in the US, I don't know for definite).
I tested out both last night as my Aunt is in a similar position and not happy about Ancestry's decision, albeit that everyone has a year to sort this out before support finishes.
There are a number of threads on the Family Historian User Groups Forum regarding migrating from FTM - see
http://www.fhug.org.uk/forum/index.php. There is a lot of help from volunteers on FHUG in getting things working but it will involve some tidying up after import.
Personally, as I've used FTM, Roots Magic, and Family Historian, FH is by far the better package but is perhaps not the easiest to understand for the new user. That said, Roots Magic's display I find rather basic, but its narrative reports are as good (although FH's can be heavily customised) as FH's.
For anyone concerned about the links between Family Historian and My Heritage, its easy to disable. And in any case, Roots Magic has the same facility that can be disabled.
If anyone has created Custom Facts/Events, then a Custom Fact/Event will have to be created in Family Historian to recognise the Fact/Event. Otherwise it defaults to a Residence Fact which doesn't look right. Its not difficult to do. The same would need to be done in any other program.