Thank you for helping Shawn. I only have the Level one course.
I have measured the home - from the front to the back of the L shape, length measures 200 (scaled). The room which constitutes the long narrow part of the L shape measures 100 (so it is half the length of the home)

Width of the home is 110, width of the room is 45 (which is almost half the width of the home) So the "missing" part is a square 70x70 - if I look out the kitchen window, I am looking at this square section which has a garden area, concrete paving and a metal shed which a tiny corner of the shed would encroach into the square area. We have a high arch pergola covering this square area on which we have covered with green climbing plants which flower in summer and lose their leaves in winter.

I can see that by drawing a dotted line to pretend that this square is part of the shape of the home, then the kitchen is exactly in the centre.

Looking forward to hearing your advice.
Stella