The best thing to do if you are only visiting your holiday home from time to time is to cancel your Skinny Wireless 4G Broadband plan when you leave. This way you stop the plan from auto-renewing and your card being charged. You will need to go into your Skinny Dashboard and press the 'Remove' button on your plan.
Your Skinny account will still be active though, so you can then simply log in again and select the 'Renew' button the next time you arrive back at your holiday home.
Your debit/credit card details will be stored to make it easy for you to reactivate your plan at any point.