I like it but I doubt you'd be able to get up into the loft. It is quite a narrow front to back so the headroom is likely to be an issue. My house is a bit wider than that and some people have gone into the loft but there is a very narrow section with decent headroom. Plus actually getting into the loft would be awkward.
Extending out the side to give an extra bedroom over the garage/utility might work but the neighbours do have veluxes on that side so might complain they are losing light.
Single storey rear extension should be fairly easy to get permission for but maybe not a two storey one.