Just checked out the Caravan Club website , but whilst they do recommend a number of devices such as wheel clamps etc , they do not actually promote any hitch locks as such .
I would suggest that you check your insurance policy , and make sure that you you comply with their requirements ! ( more likely to be a decent quality wheel clamp then a hitch lock )
This crowd are recommended by the Caravan Club for wheel clamps , but also supply hitch locks etc .
Bulldog Security Products - Securing Your World
Regards
Bern