I have bought some and yet to try them as I collect my Hornet next week.
The bullets appear to be those used in HMR ammo, i.e. 17gn Hornady Vmax with yellow Remington plastic tips.
Reports are that they are not as accurate as as other retail types, but they were so cheap that I had to buy some to try. Have a look on the Facebook page '17 Hornet UK' for more info.