Well, finally yesterday the wait was over and my new tuner arrived

http://shop.blackgold.tv/epages/BT3159.sf/en_GB/?ObjectPath=/Shops/BT3159/Products/BGT3595

Sorry, didn't take photos, was too eager to fit and test!

Installation was a breeze, just had to remember to plug in the power connector to supply power to the LNB (big warning in installation instructions to connect this)

All components and exposed caps etc are all gold - gives the impression of quality.

Fired the HTPC back up and had to manualy install the drivers for each "multimedia controller" found in device manager - no self installing utility unfortunately.

A quick reboot (possibly not needed, but force of habit) and run the tuner setup in MC again to configure the additional tuners.

Voila - All done.

Picture quality initially didn't seem quite as sharp as it did with the Hauppauge unit (using SAT - no DVBT yet). It seemed to get better after about 20 mins use, tho still a bit softer. Eyes are used to it now so I can't notice it anymore.
Channel changing is quicker
Mobo chipsets run cooler - possibly as LNB power supplied by PSU than PCI slot
CPU usage when recording 2 channels and playing back previosly recorded tv is lower - 7-9% instead of 18-22%

First impressions - all good.