My Grandfather owned one of these in Birmingham, UK in the early 1980's in order to record Open University programmes overnight.
I remember that the cassettes were reversible and fairly long playing.
I thought about this machine while browing the dead media site and decided to try a web search. I was delighted to find a UK video history museum at http://www.popadom.demon.co.uk/vidhist/
with an entry specifically on the Grundig 2 x 4 :