Keep an eye on Aldi we got one for about £15 they seem to have them in at least once each year, they also did a decent Box Hitchlock unit for £10.
To be fair I don't often deploy the Wheel Clamp as they are a bit of a faff to fit.
Our main visual deterrent is a 2m length of ships anchor chain, the links are 19mm in diameter thickness and galvanised, I thread that through the "A" Frame of the Trailer, and use a quality CISA Box Padlock.
The above is ideal for locking the trailer onto the car towbar or a nearby tree, when unattended.
A day of all things motorhome and campervan. The show is held both in the main indoor arena and across the grounds. Catering, hot drinks and food options are available. Easy access to the site and free parking included. Win one of five pairs of day tickets