Right some more investigations have been done.
I've setup a GPP policy to apply 03laser01 with item level targetting on the computername for 03*, 06laser01 with item level targetting on the computername for 06* etc.....
In the GPP I've found that not using the "run in user context" has to be used otherwise the KM4650's don't deploy.
If a computer/user has no printers it works as expected on first login however subsequent logins will give errors, If I run a delete_printers vbscript manually before logging off and then log back on again it works perfectly.
Using my existing login script for my Win7 clients is no good as the Konica Minolta 4650en drivers don't deploy to the user.