Installing the 'printer-driver-postscript-hp' package has solved my problem.
It could be because my system has been upgraded continuously without a fresh install since 10.04, but the 'printer-driver-postscript-hp' doesn't seem to be installed by default.
A brief search using synaptic, and it seems this package isn't recommended or even suggested by anything, certainly not cups or hplip.
Installing the 'printer- driver- postscript- hp' package has solved my problem.
It could be because my system has been upgraded continuously without a fresh install since 10.04, but the 'printer- driver- postscript- hp' doesn't seem to be installed by default.
A brief search using synaptic, and it seems this package isn't recommended or even suggested by anything, certainly not cups or hplip.