You have 14 days, from service of the Notice, to decide whether to (consent) to the works. If you do consent the Building Owner may then proceed with the work as advised in the notice OR

If within 14 days, from service of the Notice, you write to the Building Owner dissenting (disagreeing)

OR if you fail to respond within 14 days then a dispute has arisen (or is deemed to have arisen) and both you & the Building Owner must

EITHER:
Each appoint a Surveyor

OR
agree upon an “Agreed Surveyor”

NOTE: If you each appoint a Surveyor, the two Surveyors will agree upon the identity of a Third Surveyor. As matters proceed if you, the Building Owner, or either of the two Surveyors have any disagreements that the two Surveyors cannot resolve the Third Surveyor can determine the matter

BUT

If you appoint an “Agreed Surveyor” and you disagree with his actions there is no Third surveyor or easy means of challenging the Agreed Surveyor’s decisions without resorting to the courts using the 14 day appeal provision.

If you choose to appoint a Surveyor under most circumstances the reasonable costs will be paid by the Building Owner if the work is purely for his benefit.