What Jeremy said, if it can't be done under Permitted Development, then highly unlikely that the planners would pass such a proposal. I don't think it's a coincidence that a road like Nutfield Road, from memory, hasn't got any precedent. Personally I think it would destroy the streetscape... http://images.zoopla.co.uk/fe938c4d7eb1232d35da9085e475a747e42e4598_645_430.jpg