The cache is now filling up with lots of files of the form
../wp-content/wfcache/compton.parish.hants.gov.uk_wp-content/plugins~table-of-contents-plus~~~_wfcache.html
and
../wp-content/wfcache/compton.parish.hants.gov.uk_wp-content/themes~magnitudo~~~_wfcache.html
I would guess someone is probing the site and receiving a lot of 404s.
Because WordPress is trying to be helpful each 404 generates a unique error page so a unique cache entry.
So that's something else to add to the exclusion list except I can't afford to keep monitoring the cache for runaway conditions so I will turn caching off till the next release you promised in an earlier post.
I hope this information has been useful.