CeX vouchers are transferable. However, selling and purchasing vouchers is done at your own risk.

Vouchers are ONLY sold by CeX directly. Third parties may issue CeX vouchers as promotional prizes, however no third party will ask for payment in exchange for a CeX voucher. 

CeX are not liable for the selling and buying of CeX vouchers privately from a non CeX vendor, and is done so at your own risk