Seeking Room

I'm looking for a flexible option in London. I house and pet sit when I can but I need somewhere for the gaps in between... so, I'm looking for somewhere to mainly store my stuff and be for the odd week or few weeks, in between house sitting jobs. So although I'm totally realistic about needing to pay a regular and solid weekly amount for this type of arrangement, I need to keep it as low as possible, since there will be weeks I won't be using the room other than to leave my stuff in... if that makes sense! Can anyone help with a flexible arrangement?