I thought you might be interested in this spider seen in Pembroke Dock.
This particular spider was seen killing a woodlouse on a bathroom floor. I think this was on 31st December 2012. As I had not heard of any spider except the Woodlouse Spider (Dysdera crocota) killing woodlice, I contacted Peter Harvey the national arachnid recorder for the UK. He pointed that there are a few British spiders capable of killing woodlice. This spider appears to be Steatoda grossa (one of the False Widow Spiders) but he was non-committal as normally Steatoda genus wait for invertebrates to fall into their web rather than actively hunting them. Nevertheless, I am convinced that this was a chance encounter where a Steatoda grossa took the opportunity to grab itself a meal but was forced to retreat to the hole beside the central heating pipes without it. The website srs.britishspiders.org.uk does point out that S.grossa have "been observed feeding on pill-woodlice Armadillium. Adults have been found at most times of the year." So perhaps this is not as surprising as it at first seems.