badbadmonkey - 2:16 pm on May 6, 2011 (gmt 0)
Santa talk to a UK lawyer if it's a worthwhile cause.
Unfortunately most of the US experience won't be of help here and you don't have the DMCA on your side.
However I think the situation is fairly clear. If you have demonstrated to a reasonable standard that your IP is being infringed, the responsible party is now clearly in a poorer situation and is not likely to find sympathy from a court. Do they "need" to do anything? Well of course not, only a court can order them to do anything on fear of penalty. It's their choice to run up the damages and worsen the ruling against them should you sue.
If it seems a black and white issue, maybe talk to a registrar at your country court and see if you can extract a bit of advice. A subsequent threat to sue sent to the host with a sensible request for payment of damages, if you can substantiate them, might be enough to get their attention and conclude that discretion is the better part of valor.
Better to focus on the client in question - where are they located? Obviously, willful infringement on the part of the host would be a weaker case.