I'd like to have the dining room light controlled by its own switch, at the moment it comes on at the same time as the main room light (open plan room). Is it possible to do this easily?

I would guess that is you locate the new switch at the same location as the existing, it may not be too complicated... if you want the switch elsewhere you will likely have additional work to do.
Your local electrician may be the next best place to look...

Thanks, I've booked an expert to come and give a quote. I had a look behind the switches but decided not to blow the flat up!

Sometimes this is the best solution!

In order for us to help you, we will need more info.

Where does the power come from? One of the lights? At the switch?

What type of wire cable do you have ? 2 wire or 3 wire?

If this is a rental, would have to get landlords permission and have a licensed electrician do the work.

Chuck