It's a risky venture, as typically, the older the car the easier it is to be an economic write off, therefore, in this case, there must have been some significant damage involved. Do you have to buy this car? My money would go on something a year or 2 older that wasn't a Cat N. If you can see photos of the damage or knew the owner, it would be helpful but to buy someone elses write off with no information is too risky in my book. There is also the question of selling it on, always more difficult. I think there are circumstances where it could be effective to do this, but I would save yourself a lot of potential hassle and keep looking

Even if the write-off was recent, repair would have cost somewhere over £5K, so quite a bit more if earlier. You need to find out everything about the damage before even thinking about buying - unless you aren't bothered about resale value and just need transport.

Front-end collisions are commonest and often more fixable with bolt-on wings and the like. If it has been rear-ended that often means a write-off. Side-ons probably likewise. You say 'a dealer' - franchised ? (thought not) :-)

If in doubt, don't. But maybe ask the question about the write off, and decide whether you believe the answer.

I know somebody who bought back his flood damaged car as a Cat N and just dried it out himself.

Many more years ago I knew 2 brothers who specialised in re-shelling written off Escorts. They were of course pretty sound, but it was only economic for them because they'd had so much practice, and presumably the shells were cheap.