I assume 'webname' is not the actual name.
If they are using 'not' then unfortunately, I don't think you'll get very far with any complaints procedures, as they're clearly not 'passing off' and could argue they are making it clear they are not you.
However if there's material on their site which is a 'cut and paste' job you might have a chance.
It's a bit like a sucks.com domain being registers.
Unless the content is outrageous (libellous, etc) then merely having in the domain name is not enough to get the site closed, or to dispute the name.
Also, if the website actually included your company name then that alone might not be grounds for any case.
Take the McLibel case where McDonalds was named. Merely including their name isn't a problem, accusing food of being carcinogenic was. OK, not a website, but you can hopefully see that much depends on the context.
Without the actual 'competitor' domains to look at, it's a bit awkward to know whether you would be taken seriously. Proving they have a detrimental effect on your business might be really difficult to prove, and if they (or any other firms) can get supplies of the same goods, then it's even more awkward to see you having a strong case.
Glad you gave an example name, as you might have gone down the route of chasing them and spending money on it, when it looks as if they have little or no case to answer (on what I have read, at least).
Sorry, don't want to sound dismissive, but if www.notyou.com is the type of thing, it's hard to see a complaint getting to court (I would be suspicious of motives if some firm says they will act for you - I'd think they were just after a hefty fee).