Each local council area has differing legal requirements regarding the boarding of dogs, please contact your local council to be clear on the rules and regulations before you board dogs in your home for daycare or overnight stays. Dog walkers should also be aware of off-lead times in local parks as well as on-lead and off-lead areas in general.
You can find more info about licensing requirements in the UK here: Do I need a license to offer my services on Pawshake?