These guys do a good range of them, they will also deal with the general public even though it says [I]wholesalers only[I] but you will need to ring them, they will post no problem. Just use the drop down menus and choose a manufacturer, I know Phillips supply a good range of them, you can also get ballasts for power compacts as well from this company, the other thing they do is supply endcaps which are a bit hard to get especially for PCs.
I dont know about value
in T5 ballasts, ive yet to come across really cheap T5 ballasts in the UK, but i guess its all relative, you will definatly save a quite a lot money instead of buying regular T5 equipment from a manufacturer such as Arcadia.
EDIT: I knew i had another link somewhere
These guys are good value, shipping is good value as well.