My main suppliers of film are:

Mathers of Lancashire
Discount Films Direct
Mailshots

I've had good service from all of them, usually next day delivery. They all advertise regularly in AP. DFD and Mailshots do mixed quantity pricing - buy at least 10 films of any mixture of types & get discount.

Superia 400 is my favourite colour print film - gives nice landscape renditions, with my local camera shop's minilab. Slightly less contrast than the slower speed films. Grain is unnoticeable at 6x4".