Hi Kelvin, you have waded into probably the most contentious issue for ATCs (for me anyway) and that is the readback issue. The best I can say is to read the clearance back precisely as given. This goes for provisional clearances as well "passing FL150 route direct to XXX", "behind the landing .... line up and wait..." etc. The same for clearances with a restriction built in like rates of climb, speed restrictions at a certain DME or cross a certain point at or above/below.
Most ATCs (and we are wrong in doing this) use the time that you readback to start thinking of the next clearance to the next guy (or finishing the joke). So if your readback is short and precise, with your callsign included, it would minimise our "hearback" time and we would actually listen to what you readback. We SHOULD do this whenever you readback, but we're only human and we have an attention span of 2,3 seconds per aeroplane.
As for myself I try and do two things. I try to give the information and then the clearance like "surface wind... clear take off" and to never make one transmission with a heading and a FL instruction in it. As I say, TRY.