I assume that you want the sky box to decode the sat. signal - and hook-up to the peripheral via the SCART output (on the sky box).
That's what I do - I use a Formac Studio (
http://www.formac.co.uk/html/products/av/stud_1.htm) - but that's probably a bit over the top (it receives analogue tv as well as accepting analogue video signals) and it's £200.
If you have a DV camera with FireWire you should be able to use that (if it has Video inputs and support "passthrough" - which I believe most do).
I don't think that a DVB-S box (which would decode the Sat signal separately from your Sky Box) would work with Sky - as they encrypt everything - and I'm not sure that they use the Common Interface for encryption cards - they're very closed and proprietary.
The cool thing about recording as DV is that you can send it out to the TV again and watch the programs in the same quality as when they were shown (except that you only get Stero - not Surround.)
I use an old G4 400Mhz Desktop as my video machine and it's just about good enough - so you shouldn't have any problems.
As for disk space: DV is 3MB per second