Brake pads worn

[Cromo6555]

Hi, I have a Helium Hill300 mountain bike. Both front and rear brake pads are worn and need replacing, they are the little round black pads that have contact with the disc. Can anyone help by advising where I can buy these in the UK. Can I buy just the pads or do I have to by the full brake unit? There is a little white cap on the brakes like a bottle top with the word SunRun on it if this helps.
Thanks

 

[brucers]

Disc brake pads can be bought as an item the same as rims brake pads can. Ebay would have them as would most cycling sites. The bottle top maybe the adjuster for opening up the calipers.

 

[ianrauk]

Google Disco Brakes.