Interesting thread with some really good information - thanks everyone. I did my first ever cook yesterday and had the roller-coaster of temperatures as I played with the various inlets (2 x 3/4" with nipples and 1 x 1.5" ball valve) and also the outlets (1 x 2" standard 'hole', 3 x 3/4" with caps). I am not using an accurate thermometer I don't think, but could see that small changes take a while to kick-in. That said, I found that having 1 of the 3/4" inlets open, one capped and the ball valve about 75% open down below, and everything except the 2" hole capped up top, gave me a steady temp of around 230F once I made a chimney change:
I placed one of these over the 2" hole and swiveled it around to see how it liked to face. With this facing into the breeze, the temperatures rose (I think I was forcing more air in?) and down if I had the breeze blowing over it (sucking more of the hotel air out?) but it certainly helped when facing directly away from the direction of the breeze. The nice thing about this quick and dirty fix is that it can be quickly adjusted as and when the breeze changes - I just need to build a wind-sock for my BBQ area now!