Depends just how wet it is and how big the rhododendron is Ian. The conditions seem fine for growing a rhodie, clay soil, shade, damp etc. so you certainly won't lose anything but I would resign myself to growing shady moisture loving plants in this area unless you want to carry out a major overhaul of the area. Rhodies can grow quite big and if you plant a few shrubs like hydrangea, philadelphus (mock orange), fatsia (false castor oil plant) etc. and use for ground cover things like violets then they will love it.

Rhododendrons do like a moist soil but do not like standing with the roots in water, if the area is permanently wet you need bog garden plants.

Yes, Ian...you have the ideal conditions for a bog garden!

Some of us have to try to create it, but you have it naturally!! Make the most of what you've got...and please post photos when you've done it... :)

Or use one of the willows instead, one of the coloured bark types such as Salix vitellina - they need hard pruning yearly and you may need to chop out excess growth. They love a damp waterlogged spot.

Good point Bamboo - was so concerned to discourage Ian from trying to grow a rhododendron did not think of the obvious!