Yes, I would say the sizing is about normal - same as Next. And I'll recommend them too, they are fabulous, but I have had to sew a popper onto the velcro fasteners at the top, they didn't hold )maybe I needed the next size up!)
I've also been looking at the Dublin Thermal Waterproof Over Trousers as they have the mock suede seat which might make riding more comfortable. They're cheaper too. Hmmm..... not sure which to opt for.