Nothing about inspections other then allowing responsible access for viewings and repairs.

Hi all this is the first time I have posted here but I need advice on what my options are. We have rented this property for 3 years now and have always been good tenants. One of the issues we have is the intrusive way they deal with inspections. When I moved into the property it was agreed they would be done quarterly which was fine. Then the agency never bothered but then last year around this time they wanted to do three inspections within as many months. We were given no rationale why and when asked it was just that the landlord requested them. Then again it went quiet. We have just had another inspection at the beginning of October which the agents said was satisfactory but today have had a message from them asking to come again. I found them highly intrusive especially in such close proximity to each other. What are the rules about inspections? Can thy just be done willy nilly like this?