XPS 13 9365 Error 'No Boot Device Available'

Hi All, I hope some bright spark can point me in some useful direction.

I have an XPS 13 9365 Laptop which has worked perfectly over the last 2-3 years.

Last night it failed to boot up and shows:

    Booting from Hard Drive C

    No Boot Device Avalaible

    Current Boot Model is set to BIOS

    Please ensure compatible Bootable Media is Available

    Use System Setup Program to change the Boot Mode

Any ideas please?

(I have removed the PSU Cable, then the Battery, and reinatsted both) but exactly the same.

I had an SSD Backup Chip which I swapped and still the same.

What other tests should I carry out PLEASE?