Thanks for your enquiry and your very reasonable stance on this matter.
Unless your co-Freeholders are also as obliging as you, there is nothing legally that the neighbouring property can object or persist with if you do not agree to allow them to use the Courtyard for storage or parking. From a legal point of view, you only have to let the neighbour exercise those rights which are in existence, and just because they may require further rights to carry out their proposed works does not alter this fact.
The neighbour certainly couldn't take any legal action against you all if you did not grant consent for them to use the Courtyard for storage/parking.
I hope this assists and sets out the legal position.