The heat you feel in the top oven - the switched-off top oven can only come from below - after all you say that it takes some time and that you set the lower oven to a very high heat 200C
200C on our ovens here at home is a very rare event - just for pizza and roast spuds.
Our oven sets off the smoke alarm when it gets set to a high heat - spilt fat burns and smokes.
You might expect the glass front of the top oven to get warm if if the lower oven is set to 200C and left on for some time.
There may be a damaged or misplaced or missing seal around the front of the lower oven - that lets the hot air out.
You do not need to replace the oven - all you say sounds logical and suggests at the very worst - that the seal of the bottom oven has a problem - very cheap.
Good Luck...
January 2016