Hello again Robert,
I have good news. KB3000850 has successfully installed.
Firstly, here's my results of ls -Re -Fi "*prnekcl*" | sort LastWriteTime | ft Length, FullName -AutoSize :
Length FullName
177291 C:\WINDOWS\System32\spool\drivers\x64\PCC\prnekcl2.inf_amd64_2ff0d71af23904e1.cab
4544 C:\WINDOWS\WinSxS\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.16384_none_7efbb5a4c7db7dd6\prnekcl2.inf
9857 C:\WINDOWS\WinSxS\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.16384_none_7efbb5a4c7db7dd6\prnekcl2.cat
798 C:\WINDOWS\WinSxS\Manifests\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.16384_none_7efbb5a4c7db7dd6.manifest
C:\WINDOWS\WinSxS\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.16384_none_7efbb5a4c7db7dd6
4544 C:\WINDOWS\Inf\prnekcl2.inf
271 C:\WINDOWS\WinSxS\Manifests\amd64_prnekcl2.inf-languagepack_31bf3856ad364e35_6.3.9600.16384_en-gb_0719e7d08cb153be.manifest
245 C:\WINDOWS\WinSxS\Manifests\amd64_prnekcl2.inf.resources_31bf3856ad364e35_6.3.9600.16384_en-us_717bbf74093ca454.manifest
222 C:\WINDOWS\WinSxS\amd64_prnekcl2.inf.resources_31bf3856ad364e35_6.3.9600.16384_en-us_717bbf74093ca454\prnekcl2.inf_loc
222 C:\WINDOWS\System32\DriverStore\en-US\prnekcl2.inf_loc
C:\WINDOWS\WinSxS\amd64_prnekcl2.inf.resources_31bf3856ad364e35_6.3.9600.16384_en-us_717bbf74093ca454
183409 C:\WINDOWS\System32\spool\drivers\x64\PCC\prnekcl2.inf_amd64_59438dc7ce792b20.cab
9476 C:\WINDOWS\Inf\prnekcl2.PNF
4544 C:\WINDOWS\WinSxS\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.17415_none_7f485080c7a1ea5e\prnekcl2.inf
9841 C:\WINDOWS\WinSxS\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.17415_none_7f485080c7a1ea5e\prnekcl2.cat
7968 C:\WINDOWS\SoftwareDistribution\Download\c81c3f7fc84ac954c4736bb1c59de0fa\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.17415_none_7f485080c7a1ea5e.manifest
797 C:\WINDOWS\WinSxS\Manifests\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.17415_none_7f485080c7a1ea5e.manifest
C:\WINDOWS\WinSxS\amd64_prnekcl2.inf_31bf3856ad364e35_6.3.9600.17415_none_7f485080c7a1ea5e
I checked my c:\windows\inf\setupapi log and found out that folder/directory prnekcl2.inf_amd64_59438dc7ce792b20 didn't exist. I created it and copied prnekcl2.inf from c:\Windows\Inf into it. I ran the update again and it spent ages on 30%, I feared the worst in that it was stuck in a loop. It eventually restarted and then completed to 100%. It then spent a while on the Seattle welcome screen with the small yellow exclamation mark but let me in eventually. Everything seems OK so far.
Thanks ever so much for your continued help.
Regards,
Richard