Hi StormBrewing,
Sorry, can't help with the UK. But you may be interested to know that Croatia has the opposite situation. When we were booking a holiday there in 2004 we discovered that almost all the sites had naturist sections. Initially we eliminated them from our search as that's not our thing, but eventually we ignored the issue and the huge site we chose had two small sections of its coast that allowed naturist bathing.
For other readers, even if its not what you want to see, I wouldn't let it put anybody off going there, it is very easy to avoid those areas and even if you walk past them on the coastal path, the width of the rocks allow for it to all be rather discreet.
Mike A