the Lindy keyboard is showing as £75, yet a very similar keyboard is available on ebuyer for £18 :-O
I have a logitech bluetooth keyboard and when paired with the logitech dongle runs as a HID keyboard and works fine on the PS3 and a PC BIOS, I suspect these will work in a similar way. I can pair the BT keyboard with the PS3 directly, but it's a pain if I want to quickly plug it in somewhere else, so I pair the dongle and move that around as needed.
I also stumbled on the below links a few weeks ago, if you want some background reading! They contain a bit more info on some (all?) of the logitech dongles and switching them to HCI mode from the default HID mode: