Yes, I know. My dad is a swiss railway journeys obsessive. The true series as was broadcast on travel a few years ago isn't available, otherwise I'd have bought the lot for my dad

. He has them on tape, I mean it has degraded. However you have to transfer them to be readily watchable

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Also if you record terestrial as well as sky... perhaps a freeview PVR isn't such a crazy idea. After all ds9, enterprise etc are on terestrial on Virgin1. The PVR I mentioned can do about 300hrs of stuff and has USB in the back for your PC.
With star trek virgin 1 isn't the best channel in the world for picture quality. Although they'll be better than a degraded vhs they won't be great. A certain well known popular retailer tends to sell star trek box sets for 12.99-15.99 on a semi permanent basis and favourite seasons could be collected in the fullness of time

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Sky+ boxes are cheap speicher. Very cheap. Freeview PVRs are more but you have so much more to play around with.