Setanta did originally offer a pack that included a PCI card, a CAM and card loaded with a months subscription so I guess ESPN is still the same and you will need a CAM and a card
Reading this looks like you can get the stuff easy enough but I doubt your TV card comes with a CAM slot.
This then starts to get into the realms of getting Sky on HTPC and looking at things like Dreamboxes etc. That said I doubt the encryption is the same as Sky so might be able to simply buy a £10 USB card reader and use that ??