Sadly it is designed as a built under, removing the leg set will definately invalidate your guarantee. Not only that but the main oven door IIRC would hit the shelf in the housing. Built in ovens have a bottom lip to overcome this.
What size aperture do you have in your housing? Is it 89cm or 60cm tall?
I would have thought the best way forward is to contact the retailer, be warned there could be a restocking fee and also return carriage costs if it was an online retailer!
Don