I have a tc v8 and the absolute maximum width is 18 inches hope this helps
Ed

Hi Chris
I agree with Ed - 460mm is maximum overall width across the seat cushion.
However since the seat back will need to hinge or pivot forward to access the load space in the boat tail, the maximum width of the seat back at about 200mm above floor level should be down to 430mm (this is because the rolled edge of the cockpit side reduces the effective width for pivoting the seatback)
I also echo Paul comment, please join the club if you do become a proud NG owner.
Good Luck with your purchase - Chris

Thanks for the help chaps. I shall have to get back to the car and have a serious wriggle about!
It is obvious that the seats I have will not fit but perhaps I'm worrying unnecesarily.
Regards,
Chris