As said above, put the plates on retention via DVLA website - had to do this for a friend years back. There is a small fee, but the plates are no doubt worth it.
AT will provide guidance on retail as their 'Good Price' measure, accepted market valuations (ish)
The insurer of daughters boyfriends Corsa which he wrote off three months ago (after buying it from us
) matched what I had lined up from AT first time without challenge
But yes you can reject and have a little fun with them, if you've the energy or appetite for that though Chris.....
You can enquire on the buy back value of the car (wont be a huge amount, despite its weight as there isn't a huge demand for these I would expect compared to what is more mainstream these days) and then use the rest of the claim money to have used panels put on if a garage gives you a view on the underside repairs needed.
This latter is the gamble point though.
You buy it back sight unseen unless you can access the yard where it is stored to get personal belongings from it - the reason I used many years ago when our own car was written off...
If you can be driven there by a friendly and honest 'expert' , they could save you buying it to only have to scrap or break it yourself.