Apologies, I did miss some information out as you indicated.
CPU: 4 x Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz
Thank you for your advise.
I used to use Ramdisk until we migrated the server to pure flash disks, but have added it again to see if it makes any difference.
Apache is optimized as far as my knowledge allows me to optimize it without breaking anything.
I look forward to the arrival of 4.3