Could be that, its just harder for .uk than .com
With com etc the zone gets published so its easy to track. A Nominet member could be tracking your registrations via the PRSS. However if thats the case I would move house and get a tinfoil hat
It is more than likely people just trying anything to make a couple of quid... with the logic 'if the dot XYZ is taken I will reg ABC'
Cheers,
Rob.