Width should be the same, but will need an infill either top or bottom for the gap that will be left.
On the electric side! If it was a double oven, there is a 99% chance that its on its own supply from the main fuse board with a 30/45amp cooker switch in the kitchen as an isolator. If this is so? it will need the isolating switch changed to a switched fused spur , fitted with a 13amp fuse. This can only be done if the isolating switch is of the singe plate size.
Another alternative would be to just change the fuse at the fuse board from a 30/45amp down to a 16amp mcb.
All of the above should be carried out by a registered part P electrical installer & would not be just a straight swap.