Why would you re-visit this site after being informed of the Malvertising and Phishing link hidden scripts contained on their website let alone go direct to the scripting provider 
Remember the best and first defence for a computer on the net is the person operating it 
The website concerned sells vehicle parts, and must be used by many people some of whom, it seems, you are suggesting must have now infected their computers. I have again, today, used it directly, to order bulbs and a second time, via a fleabay link, (cheaper that way) to order more items. So far, nothing untoward coming up. So, how do I detect these particular hidden scripts?
And should I inform them that you are advising people not to use it or just that their website is dodgy?
I am no computer geek, far from it, but I do understand the principle that you put forward in your last sentence and have always tried to follow it.