We go to this site all the time, it's extremely popular and gets booked up quickly especially in the summer and Bank Holidays. Over the Bank Holidays there is a minimum stay of 5 nights and 3 nights at other times (I think this information is correct)
The site floods occasionally and therefore you have to be on site with your tow-car overnight in case of the need to evacuate. I'm pleased to say that the site has never been in danger of flooding whilst we've been there and we've been many times.
The wardens are very friendly and helpful. If you like a sunny pitch don't go to the pitches that back on to the river. We learnt that lesson one beautiful sunny afternoon where everyone else was bathed in sunshine and our line of pitches were in deep shade.
Keswick is a great town and there's a supermarket not far away and lots of cafes, shops etc, a theatre by the lake, and a lovely park. There's also lots of great walks which start at the Moot Hall in the centre of Keswick