I’ve decided to give up the unequal struggle to manually hoover the pool - too big and light/ripple reflections don’t help in seeing what you are doing.
So I need a robot.
But I know that the size (17x6), depth and shape, especially at the deep end, means that I’m probably having to look at the specialist/aka expensive end of that market.
Any advice/suggestions ??
To emphasise the issue re bottom levels I’ve attached a pic from pre new liner installation
We look after a similar shaped pool and use both a robot and the hoover as neither do the job on their own, before we stick either in the pool we use a stiff pool brush to get the debris out of the joins. Our robot is a Tiger Shark made by Haywards -
Well your not getting any younger! 
If you are buying a cleaning robot then buy one with a remote steering unit because after 3-4 hours of missing bits it will realy wind you up. These units are not cheap and then there is the refreshements you’ll consume whilst watching it 
Looks like a good pool with plenty of skimmers and a few returns but of course the skimmers can only collect the dirt when the filtration is running. When switched off dirt, leaves etc just begin their journey to the bottom and then require more work to remove them. Running for longer means less to sink to the bottom and more captured in the skimmers. Downside is you have to empty the skimmers more often 