Just to report on the final outcome. Richard Harris at IOW replied to say William Walker is not directly involved with IOW but he would pass my message on. Tonight I got a reply from William Walker to confirm the vase is one of his. He made it in 1984 when he was in Wimbourne, Dorset. It is from the "Chinese" range which he produced in 4 colourways up until 2006. So a little more knowledge to add to the list next time someone finds a pontil with a W in it.
Thanks all I'm sure I'll get the hang of this site in time now I've dared to join!