Make a loft conversion legal?

[Letsgotocornwall]

We are due to view a property which has a very dormer window in the loft and has had a staircase built too. The estate agents listing says that it as a usable space. I'm taking it from this that the conversion doesn't comply with building regulations.
I know that there will be things I cannot immediately see, (beams, etc) but what should I be looking for, as to what we'd have to do to make it comply?

• very old dormer

It will be a nightmare as it will have to be updated to current regs...

If you like the house make sure you price it in your head as a [3] bed with nicely boarded out loft space with staircase NOT as a [4] bed

We bought a house about 15 years ago, which had had a loft conversion about 10 years prior to us buying it, without regs.

Our solicitor organised some kind of indemnity for this. The sellers had to pay three or 4 hundred pounds for it and apparatnly this covered it. They said it is fairly common. It did not need to be brought up to any more current standards - of course, lots of buildings have rooms etc which were part of the original which wouldn't meet current standards, or we add-ons years ago when standards were different.

Subsequently we have recently had work done in the loft and had an ensuite put in and better insulation. We have had this work signed off properly.