FKH, I think after 20 years the developer has alternative plans with the Car Park area. Maybe in the future the MC might own the common areas. However, at thsi time it doesn't. Note the lack of cooperation of the solicitors acting for the MC. I wonder who is the MC at present and if an entity on to themselves who put them there in the first instance. The owners have little scope of individualising matters as long as the original developer holds onto his piece and to take legal action would be costly and very time consuming.
The parking is literally right behind the block, with a row of garages along the length (apartments have either garage or space), that backs on to neighbours rear gardens. The width including the row of garages is less than 10 meters, so I don't imagine much could be done with it.
Also the garage roofs are currently being renovated.
Only he could build a number of townhouses where the garages are ?? Property moves in cycles and decent developers know this. Have you spoken to other owners in the block ???