The clients printer asks for "5mm bleed with no guide/crop/reg marks" I am slightly confused by this? what does it mean? Does it mean I just have have photoshop guides? or does it mean I have no guides at all and keep that space empty?
I think you should ask the printer.. but it would appear that your document is to have a 5mm bleed with no guides, crop marks, or registration marks on output.
I would really advise instead of using Photoshop you use InDesign for a print document.
InDesign -> New Document or shortcut cmd+N
Enter print measurement in width and height:
Expand Bleed and Slug:
Enter in Bleed measurements:
Document setup example of corner:
I recommend InDesign because the last I recall to setup a bleed in Photoshop was a daunting manual process, but in reality Photoshop used for print is typically frowned upon. I would ask your client to give you the contact number for the printer to converse and I really wouldnt play the middle man game with designer to client to printer.
If you do a Google search there are several tutorials on this topic.
It is better to do that in Indesign. In photoshop u can do a virtual bleed, add guides to the document margin (just for reference) then add 5mm more to the document canvas size (10mm to the document width and 10 to height).