I would also caution you is this the best way to add space to your house? As has already been mentioned, if you do this, then you make it easy for your neighbour to do the same, and then your house devalues because it becomes a semi detached rather than detached.
Do you really need an extra bedroom, or are you looking for an easy way to add value and sell it on?
Looking at the picture, there's scope for an extension to the right, and quite possibly to the rear as well.