Rear extension

7 years ago i built a single story rear extension to my house under permitted building regs which was 3m out by 6m wide.Due to now requiring a downstairs wet room i now need to extend again which means i need drawings to scale for building approval. To make it worthwhile and making sure i build enough room to rejig the downstairs layout i feel i need the new extension to be a further 3m out and extend the width to 8m. Our house is a traditional 1930's semi detached with a 2.4m wide garage attached to the side of the house and is the full length of the house .From the photos you will see the garage is actually longer than the actual house. The new extension is to be the full width of the house and garage. I am unsure at this point if the council would allow me to build off the garage and go out to 6m from the existing and original house.
Any help or guidance would be appreciated. The build will be traditional brick faced, block internal wall, flat glass fibre roof ( may consider tiled ), no drains to the rear but would need to put drainage in for rainwater and to incorporate soil waste.Existing drain is in the garage so pretty easy to tap in. Upvc windows and french casement doors to be used.Floor to be concrete.