rizwansadiq, this is indeed a very good solution. My soldering skills are bit rusted, but I still have a soldering iron in the attic. May even have a 7805 lying around from my college days. I guess that I can do it, but will need more than a description -- a schematic will be quite helpful
As far as I understand, the above solution may not have automatic switching to battery power (when there is no electricity), and automatic battery charging (when the electricity is back). How complicated will it be if an (automatic) UPS with 12V, 7Ah battery is built?