please bare with me. I am trying to get the pictures the right way up.

I wonder, why did you describe your garden as something like bad experiment in permanently wet garden. But your experiment is wonderful. It is evident, that you found the right plants for wet soil-like for instance rhododendrons.
If I can recommend - plums usually do not like wet lands. If you need a tree just for decoration, than there are all sorts of acers (sorts of Acer japonicum for instance) which have beautiful shape, change colours of leaves three times a year and are known that they grow better on wet soils and dry them out (hopefuly my English is understandable).
Good luck Rohima.

Thank you Katarina but i am so sorry but i have to admit that this picture is not of my garden. I took the photo during a visit to the Birmingham Botanical Gardens earlier this year. I must have forgotten to put a title to it. I must say it gave me the inspiration to grow acers,of which i have a small collection . I have also started growing Azaelias and This year i planted my first Rhododendron named President Rousevelte (chosen by my husband). I am getting slowly getting there thru trial and error. This gardening web sight has been such a help and i have learned so much since joining and still learning. Thank you again for your advise. It is much appreciated.