I deal mainly with interiors. It may help if you add a few images of your property now so people can make suggestions :)

I presume that the dormer covers all of the side and goes round? You may try and get permission from the neighbour to change half the front and then change your portion of the roof to match all of yours? I notice that the side of the house isn't rendered, just painted. Therefore, that too could do with being rendered and then the whole thing painted to match, so you could at that point go for a different colour to your neighbour and include the front. Thus your portion of the house would stand out as completely different. Obviously I don't know what your dormer looks like or the exact size and position, so the above is just to illustrate and idea of the different looks achievable.

it looks like untreated pine, can thou advise on tbe material. if it is pine. you need to put a proper paint or stain system on the pine asap as it will rot if not covered with something. can you advise on the material used for the cladding. thanks Rowland

Permitted Development. Has to be in similar appearance with the roof