Brian, the cost of film is so much lower in the US it's better to order direct even if you pay the extra taxes. Kodak themselves don't distribute 10x8 any more, it's special order from KB Canham and a small number of dealers, the UK dealer "Robert White" has no Kodak products on his website.
I switched back to Ilford films because of far better availability (world wide) and am astonished at the quailty I get with HP5 in LF, I often use it hand-held for 5x4 work. Tri-X in 10x8 is around $75.99 for 10 sheets in the US, HP5+ is $99 for 25 sheets, that's a huge difference in cost and if you're buying multiple boxes a huge saving.
It's also worth looking at Fomapan, their films are excellent quality and offer even more savings Freestyle's Arista EDU Ultra brand works out $143.21 for 50 sheets of Fomapan 400, it's a thirm more for the Foma braded film. It's better however to buy from Fomafoto in Norway who are an APUG sponsor. I've used Foma films for about 6 years now and have been very happy with the results - I've not used Fomapan 400 though.