Just following on from Gordon's comments.
Obviously the two sources/inputs I have calibrated are different manufacturers but it's also worth pointing out that the Samsung on HDMI is set to Brightness = 3 in its setup menu and (due to being a digital source I believe) does not output blacker than black. I guess that if I connected the Samsung via component, the figures would be different again.
From other threads I have read, ISF calibration is a worthwhile expenditure if you can afford it.
This thread gives a pretty comprehensive description and assessment.
A DVE disk plus SpyderTV comes to about £200 which is probably not much cheaper than ISF calibration.
I decided against ISF in the short term and purchased a SpyderTV because (as I understand it) ISF calibration is charged by source/input.
Considering that I will probably be going down the Blu-Ray/HD DVD route in the next twelve months I would then require recalibration and as I now have the kit this will cost me nothing.
I hope that, if Gordon or Piers services result in a 100% picture quality (relative to the equipment) then my efforts are 80% or more although I will never know unless/until I go the ISF route later on.
Trevor