They are from a local dealer where I purchased belts before for both my JVC and various other cassette decks. I don't know where they are from though, so I ordered at set from the link you provided. I didn't get new rubber wheels, so I ordered those as well. I'll try replace both and see if it helps, thank you. 

That helped a lot. Am running some tests now, but the long grinding noise have disappeared. There is still a bit when I reverse but it's intermittent and very quick. Sounds like the two big gears that change to reverse doesn't quite line up at start. Will need to look at it later. 

I have a few questions though. 

1: Does any of the parts need re-greasing? 

2: Below is a picture of the space between the grill and where the lid opens. It's very sticky and has a lot of dust etc. stuck in it. What can I do to clean there? My guess is that it's was originally rubber and with time melted it like the belts? 

The sticky stuff is Kilopoise grease. It was originally applied to assist in the dampened opening of the lid, but is known
to creep around.
Contact cleaner (I use "Kontakt 60") and cotton buds will take care of it.

Martin

Ah great to know. I have "Kontakt 60", so will give it a go :) 

Thank you again.