To answer my own question.
Having taken delivery of CLP-620ND (£234 from Printerland with 5 years on-site warranty) I was able to download the Unified Linux Driver from the website (http://www.samsung.com/uk/support/model ... -downloads
) together with Smartpanel utility. I followed the instructions and the driver installed quite happily and worked fine.
The Smartpanel and driver configurator utilities looks horrible (compared with windows versions) but work OK.
The printer does not run native postcsript but seems to emulate OK. Print quality looks good and starts lot faster than the CLP-550N which it replaces.
I share it with my wife's XP system (and my VirtualBox XP system) and I don't think it will be going back.
(LMDE i5 64 bit)