thanks a lot for your comments and advice.
First to answer your question, the heater is an external hydor so it will be out of the tank.
Regarding the substrate, it will be heavily packed in the centre and that is how i intend it to be. Although it will be slightly smoother and deeper along the whole of the back. To be fair, at present i was more interested in getting the wood in position rather than delaing with the substrate. You are quite right, at present it is heavily built up in the centre to hold the wood more firmly while i mess with it all.
However, it will certainly not be level or even near level. The idea behind this should become apparent as i begin to plant and shape the aquascape.
Agree with your comment about moving the left in a touch. i will be doing this so thanks for that. Although still not very much. These area`s represent the boundries and cross sections defined by the golden ratio. You are quite right, it is slightly off.
Thanks mate, anymore opinions.
Chris