There are 4 options -
1. You will need to weld the old rails (Glanza) to the new seat base so you can slide backwards/forwards etc
2. Halfords sell (well did sell) a set of brakets which bolt straight to the floor then onto the new seat, but this doesnt let you slide backwards/forwards
3. Get the old Glanza rails and make a few brackets to bolt to the seat (might be a bit higher tho)
or
4. Source some already modified seat rails, Im sure there will be something floating about out there