I'm not that familiar with Nominet DRS, but if "The London Bus Station" has a name they have been using for years and have a reputation, and the Brixton Bus Station were attempting to confuse people by buying the domain - then you may have rights in "passing off" under UK tort law - something I would imagine Nominet policies to follow.
Passing of cases revolve around whether you can prove that you have built up the reputation and recognition with the name/brand, and your competitor is trying to take business away from people by confusing them as to their affiliation/involvement with that name/brand. It's a little like trademark protection, but you don't have to have registered anything.
Having a quick browse of the Nominet DRS, I would say it sounds like you have a case because "Brixton Bus Station" does appear to have made an "abuse registration" - ie. registered a name you had a claim to to the detriment of your business, and taking advantage of your brand name. The timing of registration would also be useful information here.
I am not a lawyer, but did do a postgrad in it... I'm not saying you will definitely win by any means - just that your claim appears to have at least some merit.