Not ideal...

[Niall]

You can argue it. Say Scott's car is worth £1.50 (accurate estimate there) and it will cost £2.00 to repair. The insurance will automatically try to write it off and offer you £1.50 to buy a new one.
You can either let them write it off but argue the payment they give yo (for instance, Scott's car was an immaculate example and won't get one the same for £1.50) or you can get them to repair it for £2.00 once again saying it was in perfect condition.

They have to put you back in the position you were in before the accident.

so what I said just involving maths then

Yeah. I typed it out and saw you wrote it but thought f*ck it, I'm not wasting my effort lol