Many thanks for the replies here so far.
I should have included in my post that on a Moke, unlike a Mini, the footwell space is smaller
Ethel & Stuart,,,, no, a steel wheel is out of the question !!! The one I have now I made about 2 years back after not finding what I was after and I'm in love with it. It's just perfect. However, Stuart, I do have a pair of Metro steering arms on the bench. They are longer and maybe all I need, I wanted to examine the steering geometry and any implications before fitting them, as well as just how much advantage they might offer, but at this point in time, they aren't off the menu. The units that have the motor at 900 to the shaft I agree with you, appear to be a worm drive, but I'd say here they'd almost certainly be a reversible worm (as in the worm can be driven by the worm wheel, ie, not locking or braking).
Stoney, many thanks for those links, the item from Holdens looks interesting.
Martin, many thanks for that. I found that quite interesting and often wondered if there was a hydraulic solution. In many ways, this has a lot of appeal.
Avotaz & Mike - I hear you on the torque forces and just where they would be transmitted. I'll likely be scratch making a new pedal box as part of this project and certainly, if it's a column mounted EPS I end up with, that would be suitably beefed up where the column mounts.
Tuppers, thanks for the heads up on likely smaller units. I am suspecting I'll need to make something and these might be a good base unit to start from.
Locally, the popular conversion appears to be a column from a model Suzuki which was also re-badged as a Holden Barina. I am actually guessing it's the same one as the Corsa (we didn't have Vaxhalls here, but similar models were sometimes sold on our market under a Holden badge).
If I was to go with a column type EPS, I'd like to put the motor so it ends up in the pedal box (most likely through an angle drive ?).