It can be done with a 13 amp plug & be safe if everything else is correct, but lets face it the light isn't going to be moved so it should be done as a permanent fixture wherever possible.
A little knowledge makes us all very dangerous, I understand the basics of how an airliner works but I wouldn't presume that I can fly a load of passengers safely.
Electricity can be a wonderful servant, but if you ignore it's basic needs it can turn on you in very lethal ways. Anyone that on their own admission says 'it's a bit risky' is a fool to themselves and all around them!
anyone can throw a bit of wire around and say that will do but a competent electrician saves many lives by ensuring that what he has fitted is safe and secure for the person the property & the environment that the device has to work in.
There are pages and pages of what should and should not be done I have only skimmed the surface, so if someone else comes on and says for example, "Ah yes Less but what about an R.C.D.? ETC.", then I apologise but college lecturers get more money than me so if you want to know more attend a course I'm not going to give anything else away for nothing!
Can I just get back to what I said in my first post on the subject:-
If in doubt get a qualified electrician to do the job