No, I wouldn 't have let them in, particularly since you didn't receive the notice. They sound unprofessional, particularly in their dealings with you. I'm not sure about the drive by - they may have been in the area and noticed the garden was unkempt, however they could have called you for a chat about it & given you the benefit of the doubt. If it became a regular occurence then they could have cause for concern.

I have never rented and don't own a rental property, however I would expect the gardens to be tidy/maintained, if it was in the agreement.

I understand with kids or not that a place can be messy & I would assume (or hope) that that is not part of the inspection - I'd be more concered about holes in walls, marked carpets etc....

I live alot differently to some of my friends and family - what I deem as tidy and even clean is probably not to some of my friends & certainly not to my sister (she is a clean freak!) and vice cersa, Some of my friends only clean their skirting boards once a month or even less, whereas I do mine weekly to fortnightly......

I'd check the agreement and find out what actually needs to be done/adhered to for renting the property and for inspections going forward so there is no misunderstanding for next time and also what your rights are as a tenant to let them in to inspect.

Sounds like a lot of RE agents are coping flack from vendors about the state of properties.

Whilst I agree that a paying tenant is probably preferred, I'd be mortified if the property was left in disarray and I had to fix the property so it could be tenanted again. This happened to my old boss - they had well paying tenants but when they vacated there were holes in the walls, doors taken off the hinges and it cost him a bucket load to repair, which wasn't covered by the bond.