On most sites, no, your subscription fee is only charged for the number of months your park is open.
For example, if you chose the standard package and your park is open for a full 8 months (1st March to 31st October) within a 12 month period, then you will be charged 8 x £25 = £200.00.
You can either pay the £200 subscription fee as a one-off payment once your installation is complete, or you can pay £25/month for the 8 months your park is open.
It will say upon signup if you only get charged for the months that the park is open but you have you are unsure, then please get in contact with our support.