Ah the magic of weirpools, and from a pike perspective they can be just that ''magic''.
Over the years I've fished many of them from the rivers of Yorkshire, to a few of the Southern regions rivers, and have rarely been disappointed. On occasions taking some large hauls of pike, including many hundreds of double figure fish, and a sprinkling of twenty lb plus fish.
And as has been said the weir sill's are often the most productive, from early Summer through to Christmas and beyond.
I tend to agree with Scrowell, insofar as I believe the pike must take the lures from a visual or audatory standpoint.
One tip I can offer you Matt, is to employ big gawdy Spinnerbaits, or big inline Bucktails. They have rarely let me down. I would recommend them to anyone fishing weirpools. It's great fun, PM me if you want a couple of locations.