Aside from promotional material, the only known merchandise released for sale to the general public was the Freefonix album. And there would have been a second album had the show remained popular. Sadly no second album appeared, nor did a Mantyz album as some of the fans would have liked.
However, this is a list of the various "merchandise" that has been discovered from the series. There is sadly not much.
Gallery[]
Freefonix t-shirt. It was a promotional prize in a CBBC contest. The crew who worked on the series wore similar t-shirts.
Vinyl stickers to promote the album
Freefonix album
Freefonix Official DVDs