Floor plan design for a ground floor one bed extension

The flat is an awkward one bedroom ground floor flat with a big garden. I have recently bought the adjoining garage. The neighbours have garden extensions, so precedent has been set. I want to see if feasible to convert the space into a two bed flat. I am happy with the concept of open plan living room/kitchen. I am not able to build above the garage (I believe?) because it is semi detached house and I do not own upstairs. The garage is accessed via a drive way which I own and goes out onto the garden. I am looking for some initial floor plan concepts of what is feasible with the space to determine the broad costs of the changes and if viable financially to make the changes.