I'm not entirely clear what you are trying to do here. Let me know if I've got the wrong end of the stick:
You run a reduced cell search on the CSD, or another database of structures, retrieving some hits. You then wish to filter these results according to further criteria, e.g. chemical formula, or space groups.
You can do a simple filter of the hits, assuming there are not too many of them, simply by iterating over the hits:
for h in hits:
c = h.crystal
if c.spacegroup_symbol == ...
Alternatively you can use any of the search classes except TextNumericSearch on an individual crystal structure.
Hope this is helpful; if not please ask again.