I just started the car again and moved it through the gears before checking and the level still looks high to me.

Then I turned it round and checked it - level was lower but still above the highest mark on the dipstick (and it's fairly cold today - around 10 degrees C). So averaging it out I'd say it was overfilled.

I'll try to suck some fluid out (I'll check the level again tomorrow), and see if that makes a difference.

Mike