Managed to find time to pull the DCC mainboard out to check it out and noticed some discolouration underneath.
Clean it up and put everything back - analogue cassettes are playing now with no issues 
The digital tapes are still not good - a tape I got from here just shows ‘Clean Head’ and when you press play, no sound.
Another tape plays (no error message) but the sound starts to break up.
A third tape shows ‘Clean Head’ and when you press play sound comes out but it breaks up too.
Not sure what that could be. Might be a bad capacitor vs there was work done on that board and it is residue from soldering.
OK - I will just use it to play analogue tapes then (until it doesn’t) and move the DCC tapes on to someone whose player will work with them.
Cheers
Listening to a cassette tonight and the unit just powered off.
Pressed the button, which came out for off then back in for on and it came back on.
Played another few minutes of the cassette and did the same.
Last weekend when I put it all back together it played the cassette all the way both sides.
Think it is heading for the tip soon 
I suspect dry solder joints in the power supply and mains switch. Look for dry joints at the mains connector on the PCB too. Seen that a couple of times.
Thanks and will have a look.
