I've just been sad enough to work out approximate hay prices for Oxbow from SPH Supplies, Canadian 2nd cut from Bunny Basics and timothy rich from West Wales Willows. I used the bulk ordering costs and worked it out as follows:

Oxbow from SPH Supplies - £2.50 per kg
Canadian 2nd cut from Bunny Basics - £2.64 per kg
Timothy rich from West Wales Willows - £2.76 or £2.21 per kg

I didn't factor delivery into these prices.