BBC Enterprises released the double video on 5th August 1991, but deleted it on 7th December 1993. A recent (Aug 2000) enquiry to the BBC yielded the statement that “Unfortunately, the twinpack of 'The Flipside of Dominic Hyde(sic)/Another Flip for Dominic' has been withdrawn from sale, and is no longer available for purchase in the UK.”
In 2005 the BBC released both episodes on DVD. The DVD can be bought through Amazon - if you don't own a copy go buy it right now!
It may still be possible to track the VHS video down at memorabilia fairs, or eBay, Amazon etc.
The details of the VHS video are:
BBC Enterprises Ltd 1991
Catalogue Number: BBCV 4640
Barcode: 5 014503 464028
Running Time: 176min approx
Produced by: Chris Cherry
Directed by: Alan Gibson