The 'extra' holes you see is for RHD cars.After looking at the pictures in post 9 that 9and3 referenced, I suspect the extra holes are for the Competition Seat mounting brackets, not for the eyebolts.
Remember that the Elise seats are not mounted symmetrically in the car.
The driver gets more room and his seat is more to the center of the car. The passenger seat is moved towards the side chassis beam. Both seats are also angled on their mounts..
On an RHD car the seats are 'shifted' the other way.
As the chassis' are not 'handed' (there is only one type for both LHD and RHD) there are multiple holes in the chassis in this case to accomodate both LHD and RHD seat positioning.
What people sometimes do with competition seats though is to fix the driver's seat frame (usually a fixed frame) to the car using BOTH holes to get an extra secure fit of the seat frame to the car.