Probably the place that you feel like you are at the beach and legally can get away with it these days is at Treachery - they also let you have an open fire. There are lots of other spots that you can get away with but for obvious reasons I shall not mention them here. Seek and you shall find. Remember to tidy up after yourself and smile nicely if/when the Rangers come. If you arrive after dark and clean up early then life should be all good unless you make a nuisance of yourself. Don't stay in the same place for too long though