Neighbours question: Party wall and blocked air vents

[Eleanor111]

Neighbours, with whom we get on with very well, are applying for approval to build a porch. As a result the two air-vents in the party wall would be blocked off. The specific implication for us that one of the air vents is into our larder which is underused by us - it's a bit of freeway for local mice - and which, in any case, we had thoughts about rebuilding/repairing it so that it could house food once again.

The neighbours say that if we wanted air ventilation into the kitchen maintained, they'd do it at their expense. They want us to sign a Party Wall Act go-ahead letter. My instinct is to sign - neighbourly relations are very important to us (they feed the cats ... and they're very nice people) but I'm a little concerned about the air vents. Just something about wanting walls to breath, I suppose.

ventilation of the subfloor void is important. if that gets blocked, put more airbricks along front and back walls. One every two metres is about right.

Bathrooms and kitchens also need extra ventilation.

Ventilation of other walls is not otherwise considered necessary any more (bricks are porous).

Would it damage relations if you don't sign and ask for a surveyor-they have to pay? If this isn't drawn up in a party wall agreement then not sure what come back you have if they block it up.