I've used Big Pockets for quite some time now. Maybe you gave me the recommendation a long time ago?

However, their stock of specific makes and disc types is quite random.

An alternative is http://www.svp.co.uk who I've been using for a very long time and they normally have most makes and types of media. They also test all of their media and state the dye codes for them so you do know exactly that you are buying.