Take a spur off a plug socket is the easiest and least messy solution. Hooking it into your lighting circuit is a nightmare in terms of routing cables and getting up into your ceiling, so taking a spur off a plug socket is easiest – only downside is the lights wouldn’t be switched on with the main light switch, it’ll be a switch on a wall mounted fused spur next to the socket. I believe you’re OK to do this yourself without infringing Part P rules – but you might want to check as these things have a habit of being reviewed and revised regularly.
I took a fused spur off a plug socked under my wall cabinets, was able to route the cable behind the plaster board a few inches and through a hole just under the units, so out of sight (a bit of a fiddly part and took a good few attempts, but patience is your friend here). then clipped the cable run to a 3 pin plug socket mounted under the cabinet and the lighting units plugged into that. The job looks nice and neat with all cables out of sight and works very well and are switched on via the wall mounted fused spur – though i’m using fluorescent tubes rather than LED’s. The fluorescent tube units also have switches on them so I can switch individual lights if I wanted to.
I actually use them more than the ceiling light as the ceiling light uses low energy bulbs which are useless to cast nice bright light onto the work surfaces.