Dave wrote:

I discovered that I have a couple lights in my house (and their
switch) which are run off the downstairs outlet circuit, not the
downstairs lighting circuit.

I think this was done purely out of convenience as the switch is
located right next to an outlet (yes, down by the skirting board)
though I haven't examined how it is actually wired yet.

So - Is it correct that this is incorrect? Or is this an okay thing to
do for some reason?

If it has been correctly fused at the point the power is taken from the
circuit then it is fine. (the socket circuit will probably be protected
by a 32A circuit breaker in the consumer unit - this will be too large a
rating to adequately protecting the light fitting and any wiring to it).

Regardless, since it exists, should I be concerned about this? Should
I do something like put the switch and lights on a lower amp fuse
somehow (still off the same circuit)? Or should I just leave it
alone?

You would usually have something like this before the switch:

http://www.tlc-direct.co.uk/Products/GU5000.html

Or as a retrofit, you could simply replace the switch with a fused version:

http://www.tlc-direct.co.uk/Products/GU5010.html

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/