How do you remove the microwave (Hampshire)

I have owned a 3 year old Hampshire for 10 days now and amongst other minor "teething" problems I have found the microwave is faulty. The lights come on and the plate goes round but no heating occurs! I want to take the oven out and have it replaced but can't see what holds it on the shelf or how to free it. Is there a secret or will I have to take the whole van back?

There should be four screws up through the shelf into the microwave, the heads are covered with matching stickers.