As they had already skipped a month, then you were already into 15 quid territory, so 8 quid sounds reasonable enough to me.
Seems to me that they are already turning into messers, so maybe you will need to renegotiate what they are looking for from you.
I had this sort of thing daily when I started here in Ireland in 2011. When someone said they wanted a regular clean, it really meant once every blue moon in many cases!
I'm fine with that as long as both parties understand and can work it out with each other, so I still have some of these, and it now works ok. What I don't like is people telling me what they think they want me to hear, instead of what I really want, which is simply to be straight with me.
John