So let me get this correct:
You registered the hyphenated domain and are running a genuine business from it. You have been doing so "for years" and presumably you have accounts, documents, contracts, invoices, etc to prove it. This means that you have developed "rights" in the name. It's not a registered trade mark, but it is still rights and Nominet's DRS recognises those rights.
A N Other has registered the non-hyphenated variant of your domain (after you registered yours) and they are parking it.
If the parking links on that page link to competitors or to businesses related to yours then you have a pretty good case under Nominet's DRS as it stands without having to do anything else.