Trade mark infringing domain

Just in short words, the story goes like this.

My website is X. 

Someone's else is Y.

They recently changed their site domain to be X1.

I send C&D and reports to everything I could find their presence on. It was causing a great amount of customer confusion as well as they suddenly started ranking in google with my brand upon a search for X.

So the reports finally kicked in and they are back to Y.

However, they put a redirect from X1 to Y. 

So their stolen online presence is still live and will be given the page is not returning errors.

I read another post, but I don't care to own that domain, as there are just infinite variations that could be used, but regardless time consuming.

What can be done?

Alasdair Taylor's answer to Trade mark infringing domain (2106441286)

Answer to the question: 

If you can't resolve this type of dispute through correspondence, the next stage would usually be a domain name arbitration claim.  These claims are generally much less expensive than court claims.  The appropriate procedure will depend upon the extension of the domain name.  For instance, .uk domain name disputes are handled by Nominet.  See:

https://www.nominet.uk/domains/resolving-uk-domain-disputes-and-complaints/

As a first step, you should speak to a specialist trade mark / domain name lawyer to get a view on the merits of an arbitration claim.