You could always argue that a lighting manufacturer is encouraging the use of 13A socket outlets on a lighting circuit, which is not a standard installation method.
The IEE (having just phoned them) would be surprised if the use of BS 1363 socket outlet to connect a lighting kit intended for installation in a ceiling met the requirements of BS3535 - the standard covering isolating transformers. If the kit had a transformer that could be wired into a fused spur, then that would be acceptable, but the tx is combined with a plug top, so that is out.
The IEE went on to say that they personally would not install such a kit, and neither would any pro spark. I suggested a couple of possible methods which they seemed happy with, providing there is "thorough and permanent" labelling of the circuit as "a non standard installation", explaining how the circuit is wired.
The first is to use a 3 gang socket connected to the existing lighting circuit, fused down to 3A, and plug the tranny into there.
The second would be to do away with the lighting circuit in that room, and wire the lighting off the ring via a fused spur (3A).
But, ultimately, he said he would refuse to install and advise the client to return the kit for a refund.
He also suggested contacting Trading Standards to see if there was any breach of the SOGA, 1979.