Definitely not now - if you absolutely have to move it, then wait until it's dormant. If your Acer is several years old, I'd hesitate to try moving it anyway...you could lose it.

I agree you definitely need to wait. If the acer is established you might want to consider buying another one to plant by your pond, just make sure the soil there isn't too damp and that the acer will not be subjected to a lot of wind. I still wouldn't plant at this time of year with the weather you have been having in England.

Absolutely not, Mrs MB. :-((