Nice improvement and good shots!
I had the same issue with composing as you do. Then I figured an easy trick for my night photography: jack up the ISO to 1600 or 3200 and shoot a frame with a 1-3 second exposure - whichever gets you some outlines for compositing. This way it only takes a few seconds to compose a shot, instead of waiting the 30 secs or so at ISO 100.
An added benefit is that you get a ballpark figure on the correct exposure: 1 second exposure at ISO 3200 is equal to 32 seconds at ISO 100
Thanks for the comments guys, much appreciated!
Thanks for the tip feppe, hadn't thought of that, makes complete sense! I hadn't worked out the relationship between exposure time and iso either, should be easier to work out what exposure I need rather than it being a bit hit and miss as it is now.
Thanks again, I'm learning loads!