Hi Graeme
I don't think this was probably the best scene for your test but I know what it's like when you get a new toy to play with
, I think in this case you could of done with a ND grad to go with your other filter as the sky looks a little over exposed and the posts look a bit under . Also I think if you had closed down the aperture even further to lengthen the exposure time you may of got more movement in the clouds .
Keep posting the images so we can see how you're getting on .
Mark