Happy Days !!! I have fixed it !!! 
Without the Disassembly instructions.
So here's how I did it and some things to watch out for.
You will need the BSOverture Service Manuals part 4, and part 3 will help (cost of getting dealer to do this will be a lot more than the upgrade to Gold Membership - so sign up, get the manuals and save yourself lots by doing it yourself). It's also fun - if you like this sort of thing. You will also need a screwdriver that has the right size Star Head fitting for internal screws (same as the outside rear if you want to check before starting).
1. Remove the Glass Doors by pulling first the Top Bracket off then the bottom and repeat for other side.
2. Gently prise up the LEFT black cover that is behind the left side glass - it has no screws just several plastic tabs that you can see on the diagram in Manual 3 page 4.1 "Expl. View Front" so be gentle and slowly increase force till tabs pop open - it will come away without excessive force. (You should not need to remove the right unless you have problems getting the wire over the pulley's - is a bit fiddly).
3. There is a circuit board covering the door Motor and Pulley H & G so remove the 5 star-head screws and pay attention to the one that has a lead under it.
4. There are various connectors under the board so do not try to remove it, just gently ease it up and round to give access to the Door Drive White Pulley Wheels G & H in Service Manual 4 page 5.15 .
5. Follow instructions in Service Manual 4 page 5.15 - "Mounting of wire for glass doors" section - Not the clearest instructions, as the Pulley H could do with some more detailed diagrams along with the grooves to wind round.
6. When fixing the wire to Pulley H you will push a "brass ball" end into a whole and through a slot and then wind round the Pulley H - make sure that you insert the Ball into slightly lower and right role, then up through the slot and then run wire right & down so the wire is doubling back on itself in the 2nd groove up from the base of Pulley H.
7. When fixing the other end Ball ensure you do the same in reverse - so the ball will go into the free hole and double back when wound.
8. The reason this is important is that if you go straight diagonally and wind the wire, it will not reach and you will have to start again (I found this out the hard way !!)
9. One last tip - at the end when trying to get the connected wire over Pulley P, it helps to make sure both springs are being stretched by very slightly and gently squeezing the bottom door brackets together - this gives a tiny bit more length to the wire.
10. That's the hard bit done - now screw back the circuit board and remember the wire that needs to be secured by one of the screws.
11. Now take the opportunity to clean the Black Covers, the back of the glass and refit cover by lining it up and gently pressing down evenly.
12. Refit glass the same way - by doing one end at a time i.e Top brackets together then bottom.
That's it!!! First time was a bit tricky working out the above and linking wires to Pulley H, but having done it once - it is a bit fiddly, but relatively easy job... Errm always easy when you know how.
Anyway, Good Luck and I hope this helps !
Billy W 