Installing Centos 7 to dual boot with Windows 10 on NVme drive with GPT/UEFI. Centos does not allow assignment of mount

[rwillia2001]

I have recently updated my desktop computer hardware to:

ASUS ROG STRIX Z270E GAMING LGA1151 DDR4 DP HDMI DVI M.2 ATX Motherboard with onboard AC Wifi and USB 3.1
SAMSUNG 960 EVO M.2 250GB NVMe PCI-Express 3.0 x4 Internal Solid State Drive (SSD) MZ-V6E250BW
1 x EVGA GeForce GTX 1050 Ti SC GAMING, 04G-P4-6253-KR, 4GB GDDR5, DX12 OSD Support (PXOC)
1 x Intel Core i7-7700K Kaby Lake Quad-Core 4.2 GHz LGA 1151 91W BX80677I77700K Desktop Processor
Crucial 32GB (2 x 16GB) 288-Pin DDR4 SDRAM DDR4 2400 (PC4 19200) Desktop Memory Model CT2K16G4DFD824A

I did this partly to experiment with Centos7 as a host for some virtual Centos7 minimal machines, making a toy virtual compute cluster.

However, I have a problem with the Centos GUI installer working with the NVme drive and allowing the recognition/assignment of the /boot/efi mount point. The installer does not appear to recognise that one of the NVme drive partitions must be the GPT/EFI mount partition. It will also not allow the manual assignment of that as a /boot/efi mount point. In this situation the installer cannot proceed and gives the error "Cannot find stage 1 boot device".

Background: The asus mobo bios CSM (compatibility support module) is set to "Auto" and "Other OS". Windows 10 installed without problem to the NVme M.2 drive from a UEFI bootable USB drive. Windows boots very, very fast. The NVme drive is currently the only drive attached to the motherboard, all SATA is disconnected.
The windows 10 install produced 2 partitions (p1, p2) on the NVMe drive: nvme0np1 (500 MiB) and labelled as System_reserved and the nvme0np2 data drive holding the Windows OS. I would like to verify that the 500 MiB p1 is the GPT boot partition. How can I check that this is the case?

To install Centos 7 I have downloaded the iso CentOS-7-x86_64-Everything-1611.iso and loaded it onto a UEFI bootable 32GB USB drive using rufus. This is recognized and boots to the installer options, and then goes to the installer GUI. This is good. I have shrunk the windows partition making 30gb free space for Centos7.

The problems I am having are:
1. The installer will not allocate the newly created free space to the install. It will not reclaim the free space. If I format the free space in windows disk management it will allow me to assign it as having the root mount point (/).
2. It does not recognise/label partions as sda, sda1, sda2 etc. It labels the 2 partitions as nvme0p1 and nvme0p2 - is this a problem?. It scans the drive but does not recognise that the drive has a UEFI/GPT boot partition. I think this is the critical point of failure since I cannot assign the /boot/efi location and EFI system functions.

If anybody has encountered these issues I would be very grateful for any information.

Cheers,
Roy