Sadly John Boddy at boroughbridge sold up and then closed down.
If you're in North Yorks then Duffields at melmerby are a good source. Also Scawton sawmills near Sutton-under-whitestonecliff. Further away there's Snaiton. Or at Doncaster there's Turners retreat.
Styles and Bates, down south do mail order and come highly recommended.
However ply and laminating as per Jason would be your best bet I think.
If it can wait and you're local the Northern Woodworking expo at Harrogate is on 20-22 November and there's always a good choice there.