Not sure Hale’s do turning blanks? If you’re willing to travel a bit, Wentworth usually have a good selection of blanks. If I remember right, Toolite in Mitcheldean had a few blanks, but it’s not something they specialise in.
...sorry, should have read your question properly, I just assumed turning from “blanks”. If you are after slabs, wentworth are still the best if you want to browse. If you want oak, Whitney Sawmills are reliable in my experience (I only buy sawn, they may supply PAR). Most general timber places will have PAR stock. Have you tried Griggs in the Bristol road? They have quite a bit that you can choose from. Stored outside in open sided shelters though, so bear that in mind.