We use the staff at Animal Choice vets (Upper Tooting Park road) for cat feeding when we are away. No recommendations for house sitters .... Although would gladly sit for you and leave my toddler with my husband, but not sure he'd go for that!
I've got a very reliable friend who does occasional house and animal sitting (cats, dogs, guinea pigs and horses to date!). I'll PM you with her contact details. She can provide you with references from previous clients.
Can I just recommend paws at home. Christine has pet sat for us for almost 5 years and is very reliable even on short notice and a real pet lover. We've always come home to happy pets!