Yes we have. My H is a prince(ss!) and hates public swimming pools so it was something he particuarly wanted and I did like having it. Also my youngest DD doesn't like to swim for as long as her sister and so it was nice to be able to go back to the cabana for a rest with her. We paid £35 and tried to get one for the other days whilst we were there but they were all booked up.
We like to get the swim out of the way on a morning so we are freed up for the rest of the day and I noticed at Whinfell that the main pool opens early for families with children, therefore we managed to get in before the 10am rush and find a decent base anyway. If you can see yourself getting there as early as 9.30am and doing the same you might find no need for a cabana.
Yes,we did this at Whinfell and it was good,great for getting the children dried and fed,and good to have a base as there was eight of us. Don't recall what we paid for it but we said we would do it again if there were a few of us.
We went to whinfell in feb. We used a cabana once. It was handy to have as we have a baby who didnt spend as much time in pool as older ds. It had a safe, free cold drinks, towels, tv, inflatables, highchair.
I would say if you can get a good price by booking in advance then do it. We paid £50 which I wouldn't do again.
To be honest once we're done swimming I just want to get out, always feel a bit itchy with the chlorine and it's warm and damp in there so horrid for sitting around. I think i might book one if I was with a big group who were spending a few hours in there so we had a base, and particularly if we had elderly or small babies etc with us. They look ok but you can't change or shower in them or anything useful really.