the development plan or current development plan shall as respects that district be taken as being whichever of the following plans gives rise to those assumptions as to the grant of planning permission which are more favourable to the owner of the land acquired, for that purpose, namely the structure plan or, as the case may be, the Greater London Development Plan, so far as applicable to the district, and any alterations to it, together with the Secretary of State’s notice of approval of the plan and alterations, and the old development plan;

land situated in an area defined in the current development plan as an area of comprehensive development shall be taken to be situated in whichever of the following areas leads to such assumptions as are mentioned in paragraph (a), namely any area wholly or partly within that district selected by the structure plan or, as the case may be, the Greater London Development Plan as an action area and the area so defined in the old development plan.