[entwisi]

If they allow you to buy it it will be clasified as either Cat C or D (C being worse than D) Insurance companies do load policies for cars that are previous Cat C/D write offs. Also remember that effectively it's future resale value is peanuts as a HPI check will show it as a previous write off.

They are legal as long as it passes an MOT. You can use it withouut fixing as long as it doesn't have any sharp edges etc and all lights work correctly etc.

One thing that may have happened is that the boot floor may be twisted. This can affect the tracking of the rear wheels so make sure you know what you are doing if you buy it back with a view to use long term.