Thanks to SFE, martymexico, Flighter and Drewdog, your help is invaluable to me and really appreciated.
Best regards,
Paul

I believe early Mk2 Escorts used a short steering shaft and a long coupling, later cars the opposite.
Mk2 microfiche parts list shows
Steering shaft to 8/78 Part No. 75AB 3525 AF
Steering shaft from 8/78 Part No. 77AB 3525 AA
Coupling to 8/78 Part No. 75AB 3B763 AC (without sports suspension)
Coupling from 6/77 to 8/78 Part No. 75AB 3B763 BA (with sports suspension)
Coupling from 8/78 Part No. 77AB 3B763 AA (without sports suspension)
Coupling from 8/78 Part No. 77AB 3B763 CA (with sports suspension)
Long time since I had an Escort but fairly sure Mk1 couplings will fit Mk2 with short coupling and they had more robust fabric joiner.
I wonder if Gp4 couplings would pass a roadworthy.
 

Escorts from late 75 mk2 to early 77 have the longer steering knuckle... My guess for this is Ford had so many blank steering shafts from the mk1 they decided to just cast a longer knuckle till the slightly longer (bit over a mitre) were produced and carry on as normal.
As to what uni joint to get is up to you. I used to work at Quickco Motorsport (Escort performance heaven in the 90's) and sold both types and never had complaints .
Will it pass a roady.... It should .. Whether it's a collapsable rule but can't see that... You'll be fine..

Hi martymexico,
I've had a look around and I think I will order the cast short coupler from Burton's. It looks to be good quality and seems like it may be my best option. I've bought a few other items from Burton's and have found them pretty good to deal with.
Thanks again for the help.
Regards,
Paul

Only problem with ordering from Burtons and other O/S retailers is that the freight cost adds considerably to the price of a single item making it rather expensive. Need to do a small shopping list of other items/spares to lessen the cost per item. You know, hoses, cables, gaskets etc or a group order perhaps.
SFE

You're  right SFE,  I have been caught out a few times in the past having to pay silly shipping costs on items from overseas so I will definitely have a good think to see what else I need and may be able to order at the same time to minimise shipping costs.
best regards,
Paul

If only ordering a single part I have had success with Mike from Yesterford. Unsure of how his pricing compares but he’s always been helpful and maybe worth considering?

Thanks Paul,
I haven't ordered the coupler yet so I'll definitely contact Mike for a price including shipping.
Best regards,
Paul