I wouldn’t pay £8 an hour for a pet sitter.
My dog walker will come and look after nooch as normal during day and then come at bedtime and stay overnight with him. He charges me an extra £10 for staying from 8pm until 8pm in morning. Although I do provide a meal for him!!
It is £8 to put your dog in kennels overnight in our area so £8 an hour is too expensive. I would say you should advertise as – price depending on requirements. That way it depends on how long you are required – whether it is during day when you could be making more money by walking or if overnight stay when you wouldnt be earning anyway?