Again, don't get too dismayed, the recent wet weather has shown water retention problems everywhere, even our allotment lane is flooded, and that drains directly into a stream about 8ft below the lane. The decision about changing plots must lie with you, but if you decide to keep the current one, you can improve drainage by digging a trench around the edge of the plot, this will divert water away. That may sound like a big task, but it is not that bad really, if done in stages.
Whatever you decide, keep smiling, and good luck :D
Derek