When told to got to a FL our company changes to STD, however the SBY ALT remains on QNH until through FL100 on the way up. The reverse happens on the way down. So you have visibility of both FL and ALT. The problem as already mentioned, on a low day out of BHX, with trans ALT at 4000ft and block FL of FL60, you need to go over as soon as cleared else you will bust. And the issue with this is that this part of airspace to the south of BHX would be one of the busiest in Europe, so you cant afford to mess around. True a transition level of 10,000ft may be suitable, but when you have significant terrain at many destinations, and also with a higher ATC work load It is much easier for a controller to say climb FL70 than seven thousand on QNH, especially if the QNH is changing rapidly which happens in the UK and you pass through 6 zones before crossing the channel. In Australia where you efectively have two area controlers outside of the TMA, ie MEL and BNE, it is much simpler. Imagine trying to handover in london to state ALT and QNH. Its hard enough to get a word in now. For the moment, I can handle setting STD and monitoring ALT on the SBY.