Thank you Olaf. You seem very knowledgeable about bananas. I'm a novice as you can probably tell. I thought I'd have an easy job with the Greek weather on my side but I underestimated the difficulties.
Indeed I had not removed the old pot soil. I removed much of the new soil today and replaced it with neutral soil. I could not remove all of it unfortunately as some of it was placed directly under the banana.
She seems to be worse today, and the brown patches have expanded. I have uploaded an image here
Banana Gallery - unhappy little basjoo:
It's funny how one of the leaves has got those small spots that look like freckles caused by the sun. Our skin and plant's skin seem to have similar reactions to the sun