Apparently home cinema doesn't work in the UK
, but no, I don't know of any preamp able to output individual channels, or pairs of channels, from a surround mix in digital form.
Were you to want to do it in analogue, life would be considerable simpler, as there are a few surround processors out there, and more than a few AV receivers, with multichannel analogue preouts.
Not sure how you'd do the centre channel, though...