Hi Andy,
Interesting little project, nice hull with a shallow keel ideal for ponds with weed ! any idea what it is ?.
I also used Modelling Timbers and now use Jotika in Droitwich for similar timber stock,
pitch pines not listed on his website - but they produce high quality static period ship kits, might be worth a phone call.
Mantua Models also stock similar timbers including Walnut dowels, SLEC are another modelling supplier.
You may be lucky in B&Q's/Wickes etc Richard Burbidge rack of moldings/dowels -
finding something straight without finger joints will be the difficult !
Noticed a new addition in B&Q recently - a handy cardboard box containing metre lengths of small sized 'straight' strips of timber,
stacked vertically on the floor near the main moldings rack - could be planed to shape. Paul