I was in London last week and saw Show Boat at the New London Theatre. It was a wonderful production based on the Goodspeed Opera House revised version from a few years ago. If you are in London, or going to be visiting any time soon, I would highly recommend it. The casting, singing, dancing, etc. are all top notch. It is presented on a thrust stage and there is really not a bad seat in the house. Gina Beck is a perfect Magnolia and Rebecca Trehearn will break your heart as Julie.
I saw it as well two weekends ago and really enjoyed it. My only qualms we were two of the actors had such bad American accents it really distracted me. I'm sure English audiences always laugh at broadway English accents too.