Neighbour’s Right to Enclose and Compensation Under Section 11(11)

Question 

I have a semi-detached property of which the adjoining property is and has been derelict for some 25 years. The owners have been in family dispute for some time.  I have over the years improved and developed my property, whilst always ensuring the correct procedures  i.e. party wall notices etc. 

I have extended the front of my property over 2 stories out to the building line, and in doing so I have extended the Party wall out through the adjoining chalet style roof with a parapet style coping to the top and added a pitched style roof to match our dwelling as required by planners etc. 

If the neighbouring house eventually gets purchased, am I right in assuming that if they wanted to mirror the development that I have undertaken,  they would have to offer adequate compensation i.e. 50% of the cost of building the extended party wall element to allow it to become enclosed.  At the moment is it not a party wall as it is outside the internal habitable element of the dwelling? 

If the wall is wholly on your land then your consent will be required and compensation will be by agreement although the Section 11(11) equation is normally considered a fair solution.