Disappointed with noise levels....

It's your metering then - not the ISO per-se

Don't forget that an ISO400 shot that is 2 stops under exposed is actually ISO1600. So, if you had to push up the RAW conversion exposure - your 'pushing' the noise as well.

The more you pull stuff out of the shadows, the more noise you'll get - at any ISO. It's a bit like a radio transmission - if everything is transmitted loudly enough then you'll get a good clean signal. If you crank up the volume to listen to the quiet parts at the same volume then you are going to get more noise.

With night shots like this you should really work in "M" mode. On matrix metering the camera is going to see a LOT of black with some very brightly lit parts in the middle. It's almost certainly going to get this wrong! Use manual mode, and spot metering - meter on the part you want as mid-grey - then take the shot. You'll probably have to bracket or shoot & test to get it right.

Failing that, with such a wide range of highlight and shadow, you'll have to go the HDR route and fiddle about in software!

Hope that helps!
Matt

this has all been very helpful and a great bit of learning for me.... thanks all for your time on this. much appreciated.

Still learning about all of this photography malarky, but loving it!