Thank you so much moderator, incredibly helpful (and so great that you are on these forums helping customers, really appreciate it!!). As noted, we don't have a dealer in the UAE, so no one to really ask!
On that basis, it seems like my best speaker placement would be as attached - do you agree? I have moved the height speakers wider from the listening position as suggested. This means that the 2nd set of center speakers would be level with, or only slightly behind the listening positon (as otherwise, as you can see, would need to go much closer and looking at the information on the GE website, this is probably as close to that as I can get).
I have also pushed back the rear HTR7,000s to 4.2m (13.7ft ) back from the listening position. Do you think that is enough, is there any maximum you can go - I could probably go back another ft if needed, or can equally come forward, it entirely depends on what is best.
On that basis, given my height is around 3m/10ft, I will go with all HTR 7,000s. Thanks for the suggestions on the amp too, there is a new Marantz amp out, the 7012 which looks like it would do the job I need (and allow me to turn into a 7.1.4 system at a later stage with additional components if necessary).