Ask HN: How to deal with someone ripping off your design?

We recently noticed that two websites have recently ripped off the design, code and copy of our site, gocardless.com.

How did we notice? We started getting Sentry errors as they had even gone so far as to rip our JS files!

Before we get in touch with them, we wondered if anyone had any tips on getting these guys to stop.

Sites in question:

http://secure-broker-online.eu/ http://resinternationalgroup.com/