You do not say whether you would consider boat tent but here goes
My favourate palce is Loch Lomond. On sailing; If you have an O/B.you have to register.Free but you have to buy or paint same on a board. Slip and go in Balloch and parking car and trailer Is free With no time limit.
Loch is 25 Mi. X 5Mi. with about 38 islands Sandy beeches (no mud) Plenty of sheltered bays.We go for a week every year Mooring at a different pub for a meal every night.
If you want a camp site I would recommend Millaorchy bay.Two slips.One into Bay with jetty.Other with on jetty but you can pull the boat on the L/T.and leave on the beech.
I also sail on Ullswaterand Windermere.
Give me a ring if you require more details.01228560085.