I recently helped a friend fit one, 4ftx2ft, in the kitchen of a house in California. It was designed for surface mounting on a ceiling, and had a neat bezel. The back of the panel was a zinc-plated steel sheet, which served both as strengthening and heatsink.
I found only two issues:
1) the condition of the 1940s wiring (and those horrifying wire nuts - don't go there!),
2) the mounting system required pretty accurate hole placement on the ceiling - this is harder to do than you might think, especially if your head no longer tilts up as it should!
To cope with (2), you need to know what's above the ceiling with some precision. Most sparks just lay cable for lighting where it will fit, as that is far quicker than setting it out in straight lines parallel to the walls (and the latter is usually unhelpful anyway). If it's gypsum board (plasterboard) or similar, you have fixing screws along the joists, concealed by plaster. If lath they will be long tacks. These you can find with a metal detector, and you can also probably map the route the cables take. As you will be drilling for fixings, this is important. I would mark what you find on the ceiling in soft pencil, so it's unambiguous.
Then there is the ceiling construction: if lath and plaster, it isn't flat. Panels don't bend, and anyway they do need to look neat, so you will probably have a fairly awkward scribe to do.
Finally, on the one we had, the only cable entry point was dead centre. This was awkward for various reasons: obviously the ceiling rose was _not_ dead centre, but not least the difficulty of connecting it up before the mountings were fixed.
I had limited time and limited resources available, but one thing that would make this much easier would be thin lighting flex. that would fit behind the panel, say 1 metre extra, to allow you to manoeuvre it.
LED panels don't need much power (e.g. 60W is only 0.25A at 240V), so the heating effect spread over 8 sq ft is tiny. You don't need heavy-duty flex, but three core (so you can maintain the earthing) is sensible.
I've no doubt there are better panel designs out there (and ours was made for the US market anyway), so if you haven't bought it yet look for one that gives you the easiest fixings and cable entry options, or room for flex to be hidden behind it.
HTH, E.
PS: If you can't get all the fixings into the joists, I think "cavity fixings" such as "Intersets" are perfectly strong enough for that application. Obviously use the ones that allow you to remove and re-insert a machine screw or woodscrew, otherwise you can't do a test fit! You can also wood-glue blocks or plywood plates on the ceiling (above, out of sight) over your anchor point, and screw into those - that's really strong too. I've done extractor fans that way, to protect the plasterboard from crumbling.
