Not sure if long-term parking in Helmsley is a viable option, as I believe the Car Parks are expensive. However, as I have a little local knowledge, I'd park my car in suiatle side-street. There is a turning almost opposite the BATA petrol station 500m East of Helmsley on A170. Turn (N) up there and ther is another oad on you left after about 100m. From memory, this is a quiet road of detached houses. Nice and wide. A car is unlikely to come to any harm. (The locals may even kepp an eye on it for you).