Thanks for your replies. I have also read the “DNA hope” thread started by Wulfsige and found it very interesting, as my paternal family name brick wall is around the same time as his, and DNA will be very low. I have done most of the things suggested there, including a spreadsheet matrix of matches, and uploading to Gedmatch. I know that any one case of low level DNA won’t be proof, but am looking for clues in lines I can prove by doing my own research beyond pre brick wall dates so that I can steer my own old style genealogy to the right places to look. Match clusters may help in this. If I can get a good set of matches pointing to one branch or location I will be happy.
So, I am doing what Biggles suggests and using DNA matches which have my family name in the linked tree somewhere to build trees to see if that reveals a common ancestor or at least common locality of origin. In my case I am putting the individuals on WikiTree, so they aren't really “my” tree and there is also potential for links to Gedmatch there if users have uploaded their DNA to that site. It isn’t easy going, but I am getting the hang of it.
On MyHeritage I will take up Glen in Tinsel Kni's suggestion as a way forward and upload a Gedcom from Ancestry, reassign my DNA test, then delete the old. That was something I wasn’t sure I could do.
Yes, I agree, many of the matches, smart or dumb, and hints and recommendations can be a real pain. I wish they could be filtered in some way. There is occasionally a nugget somewhere, but often it is just a photo or document I originally put on from my family collection coming back to me as you mention, Biggles, even across sites, or a heraldic crest far distant from the world of Ag. Labs. and Weavers that populate my tree for the most part.
My winge over, can I just mention that I did do a Y-DNA 37 marker test with FTDNA as a toe in the water. That just proved it would be pointless splashing any more cash in that direction as there were no matches that included my family name and the only close match at that level didn’t know his family history at all. I have enough strong paternal line autosomal DNA matches to know it wasn't a family name problem. It was a gamble.
If any of this works, I will post it.
Thanks to all.