Actually the slipway is not free here pete. Users have to pay the harbour master for the use of it and the river.
Im not sure if this can be done as a day ticket or annual harbour dues are required.
Also, the carpark is no longer free, it was, up until the start of this year when the council decided that because people were staying at home for the summer and paddle boarding or kayaking more, they would charge and make more money for themselves!! Its the same at the carpark west of Lee on Solent.