For the poll to be the highest point is the AIM of the training - you work towards it building up enough strength, balance and carriage.
Therefore its obvious that, especially, in the younger horse there will be times when this cannot be achieved consistently.
Many photos in H&H are taken...
If you don't mind a horse a little bit bigger I may have just the horse for you!!! he would be around the 16hh mark.
A friend of mine is looking to sell/lease/loan her 17 year old plodder .. he has more in him if you really want it and ask for it - so always a little bit more if the rider...
Have you looked at the British Dressage website? That should give you alot of information about what they are doing in your area etc.
There is also the chance to try out for Teams which is really good fun!