From a cursory look two possible solutions:
Make sure your priorities.xml file for the folder/system ZX Spectrum does use screenscraper first, then gamesdb, then import for the title.
For manual import you need a template (definitions.dat) with all ###xy### strings (including ###TITLE###) and a actual XML-snippet with the concrete values. The only differences between the template and the XML-snippet must be the the ###xy### strings and the concrete values. Keep withspaces, no reordering, nothing. And -but I guess you did- the file to be imported must be named like the romfilename but without extension.
HTH
PS: Good to see you solved it just before my reply. :-)