Connection between new timber frame and existing stone building - help!

Hi all, 

We have planning, building regs approval, and begin works in March. Almost all details and head-scratchers ironed out, apart from the topic of this post!

We're extending off a gable end of a rubble-stone cottage, with a timber frame, timber clad extension. On two parts, the frame/cladding will need to fix to the existing cottage. I'm still scratching my head on how to best do this, in a neat and weather-tight way. 

I've attached some screenshots of the plans which show the joins:

A: This shows the more complicated join, where the old cottage and the new extension come together at an angle. The join ideally needs to be flush(ish) rather than cladding lapped over the cottage. The secondary head-scratcher here is that we have to (thanks planners) render the new timber frame to the level of the bottom of the ground floor windows. This render will sit approx 40mm shallower than the timber cladding above.

B: This shows the same as A, but from the side. 

C; This shows the simpler connection on the other side of the house, where the connection is an internal 90º. For this we can but the frame up to the house, lap tape/dpc whatever we need around timbers and battens and then carefully cut the last boards to fit the cottage. 

Any thoughts on methods of how to connect these in a good, neat, weather-appropriate manner (ideally with first hand experience/photos/drawings would be greatly received!! 

Please no comments on "why is your window that size" or "why doesn't this line up with that?" 🙏

Thanks!

Joe