IN NSW the relevant part of the act is
65 Can an owners corporation enter property in order to carry out work?
(3) In an emergency, the owners corporation may enter any part of the parcel for those purposes at any time.
(4) In a case that is not an emergency, the owners corporation, may enter any part of the parcel for those purposes with the consent of any occupier of that part of the parcel or, if the occupier does not consent, in accordance with an order of an Adjudicator under section 145.
So in a non emergency situation the Strata can only enter your lot without your permission if they have obtained an Adjudication order allowing them to. So next time basically tell the guy he arranges a time that suits you or he gets an adjudication order.
This applies to the Strata as you are a tenant the owners can gain access based on the tenancy agreement.