I am currently in the process of obtaining a pc card to use with progdvb but have a couple of questions before I go ahead.
Firstly, I subscribe to the sky sports package but am not currently subscribing to hd. Would I be able to subscribe to sky hd without a sky hd reciever as I have heard they wont open up the channels unless you have their reciever?
If this is so, would progdvb then be able to allow me to view those hd channels?
I am thinking of getting the skystar usb 2 hd. Would this be a good choice or can anyone recommend something else?
Any help would be greatly appreciated.

This is a very Britain specific question...

You should know, British Sky Digital uses a very secure encryption, NDS / Videoguard.
For this, subscriber cards are married with a single receiver each, by use of it's serial number. AFAIK, there is no NDS / Videoguard CAM on the market (yet).
So, if Sky HD is scrambled, it's not supposed to be working with any PC based DVB application. SD quite similar...

What's even worse, many HD stations use DVB-S2 transponders, that require special tuners and compatible software, also including MPEG4 / h.264 decoding and a really powerful CPU and / or good hardware support from the VGA card.

Find out more on stations / transponders here:
http://www.lyngsat.com/28east.html

You may find other British users at dvbn.happysat.org, for example.
But I am in severe doubt, they could help you any further on with this...

The SS2 HD can't tune to DVB-S2.

So how can I watch sky on my pc with a pci card (remembering that I am a sky subscriber)?

Sorry, but AFAIK you can't, until someone brings out an NDS CAM (or emulator).