Pauly, cannot help you directly sorry but we have just got permission for our single storey Granny flat to be built.
No solicitor involved just an architect and a few trips into Stara Zagora to get a few papers stamped etc.
We paid 900 lv for 50m2 or 18 lev per m2 and then a few hundred on top for muncipality, electric and water fees.
350 lev for geocid report and buiding control inspections.
This includes full plans and permission.
Hope this is of some use.