Thanks folks. Looks like i was not detailed enough in my question.
The rolltop was not laminated by me, so it's a fairly standard wrapped edge.
This picture is from underneath on another section.
It has some kind of plastic sheet on the bottom, which overlaps the laminate by 1/2" or so, you can just make it out in the picture. The picture is without drawers fronts fitted, so this is what would be exposed when opening and closing the door. As you guys said, it's whoosh of steam and moisture when opening the door at the end, and when my wife suddenly adds things half way through the cycle, that cause moisture.
You can see here better the protective covering
A friend said the protective coat starts to bubble and peel after a while, so I should use some aluminium tape to protect it. If there's no particular type, then I guess anything is better than nothing.
This photo shows I'm starting to get some peeling in that area, hard to make out this picture so I added some reference arrows, from the bottom that's underneath of stretcher with plate installed, front of stretcher, underneath of top, front of worktop.
You can just see against the dark edge, close to the join, a sort of flaking, bubbling, peeling effect. (Yes I also have a hole to fill with PVA!)
I also have that metal plate that came with my Bosch, which you can see installed further under flush with the front of the unit.
I think I'll just get whatever I find in my local box store unless that's madness!?