What a lot of posts on a relatively non-descript topic. I am a bit
at the hatred shown towards LL (accidental or otherwise) on here. I will add, too, that my DP is a long-term renter (20 years plus) with a crappy LL, so I can see it from both angles.
@Thankunextex, I agree that the LL should have sorted out viewings in advance, if s/he didn't do so.
Just to throw my lot into this... I let out several properties, and am in the process of selling one. Those on ASTs have a clause saying that I, or anyone else acting for me, has a right to enter the property - with a minimum of 24 hours' notice. I don't have an agent (because IME, they are not as efficient as I am). The tenants in my property for sale are happy to allow viewings, with notice. I don't expect them to clean the house in the way that I would for a viewing, and have told them so. My house sale is not their problem.
I have had only one shitty tenant, in 25 years of being a LL, who insisted on the 24 hour notice period when the central heating boiler broke and he was freezing. I sorted out an instant repair, but said tenant then refused access to the British Gas man on the grounds that I hadn't given him 24 hours' notice. 
So while some LL are undoubtedly shits, this is also true of some tenants.
OTOH, most LL and tenants are, happily, both lovely and willing to meet one another half way. It seems you have copped for some unfortunate ones, OP. Don't give up, though, if you love the house.