dvi-d hdmi

Yes, however, it will not contain audio information and will only be a means of conveying video to your pretty tv. If you have a receiver in your home theatre setup, that should not be a problem, since you'll pump the audio directly to the receiver, not the tv.

Well 5 meters is probably about the point at which it matters about cable quality. But for the price, heck that's almost worth just trying and seeing if you get sparkles or darkening.

It's amazing how little cable length matters for HDMI, but 25 is starting to push things where likely some good insulated low noise cables might become necessary. Do you need 25ft? If you can use just 15ft you should be fine even with bargain basement cables.

Not sure who sells what in the UK.