Can anyone suggest a suitable place to buy decent die-grinding bits? I cant find anything anywhere....

I need some decent ones to go in my "aldi special" air die grinder...

Depends what you want, try googling 'Rotary Burrs' and 'Rotary Files', 1/4" shank grinding wheels etc.

I got some on ebay for not a log but I havent used the yet. die, burr etc as suggested! You sometimes find ones which have been used for CNC and there is a ring thats worn and the rest is as new, fine for porting and stuff!

Cromwell sell good quality rotary burrs.

http://www.cromwell.co.uk/category_page/09020201

and mounted points (the stones), later pages have the die grinder ones rather than the 'dremel' ones.

http://www.cromwell.co.uk/category_page/090503

Make sure you get the right size shank, most seem to be 6mm but some are 1/4". Unless you have the correct one to compare with or a vernier to measure with it's difficult to tell as they're so close & they aint really interchangable.