In reply to EddInaBox:
Paul has just confirmed that UKC do legitimately use that address but I think it's worth explaining why it's not a suspicious address in the first place. The important part of the URL to look at is the *final* bit before the ".com"/".co.uk". That's the domain. Anything extra before the domain, like the "go" in this example, is called a subdomain and is still controlled by the owner of the domain (unless they had been hacked themselves). It's quite common for websites with lots of outbound links to redirect them through a specific subdomain. It's also common for adverts or images to be hosted from their own subdomains.
I can't recall which specific subdomains UKC actually uses but as an example...
"ads.ukclimbing.com" wouldn't be suspicious and would be controlled by the owner of "ukclimbing.com". On the other hand, "ukclimbing.ads.com" would be controlled by whoever owns "ads.com" and would be a suspicious address to see when clicking on a supposed UKC link. (This picture is complicated by the fact that most websites have their adverts, and often images and other media, externally hosted.)