Update 3

No mention has been made of the other steering gear problem - that of removing the old bushes from the centre arm.
When an attempt was made to remove the bush at the end of the steering arm, no amount of persuasion, gentle or otherwise, was successful despite the use of a variety of tools that should have done the trick.  The next option was to remove the steering arm from the steering box shaft that is splined and conical.

The question was, was removal of the arm necessary?  The answer had to be 'yes' because the arm position did not allow the steering wheel to be aligned correctly unless the track rods were adjusted to have unbalanced lengths.  This imbalance was about 0.75 inches (about 20mm) and did not follow the Fairthorpe guidelines of being of an equal length although we have since learned that none of the EMs achieved such a result!  The length imbalance can be seen below.

It is obvious that unbalanced track rod lengths will affect the steering lock and so the decision had to be - remove the steering arm and then it can be replaced in such an angular postion that track rod length balance can be achieved.

Like the bush that could not be removed, the steering arm refused to budge and so the decision was made to seek the services of a local motor engineering firm having a good reputation as well as the requisite equipment.  The complete steering assembly was removed and then returned with all bushes and the arm removed.

Problem solved?  Yes and no because removal of the arm revealed that the shaft/arm junction was not a simple splined cone that would have allowed an incremental angular adjustment of the arm but also included four wider and deeper splines that effectively limited angular adjustment to 90 degrees thus giving only one position that was useable.

Two of the four splines can be seen on the image, one in line with the hole on the threaded part of the shaft and the second 90 degrees clockwise from it.

Update 2

Here is an image of WEW 707 in June 2009 after being neglected since 1978!
In fact, some remedial work had been done as the tyres and inner tubes had been replaced to allow the car to be moved.
The badge has been removed as some of the enamel had flaked off.  Strange to relate, the enamel, when the badge was installed in 1959, was white but when a replacement was obtained, the enamel was blue and we were told that all the Fairthorpe badges were blue!
This year, as soon as the cold weather started to give way to something more in keeping with car restoration, the hydraulics were tackled and the first setback was that when an attempt to remove the slave cylinders (two per front brake) was made, it was found that the unions behind the front brakes were locked solid.  This resulted in damage to the Bundy tubing when the unions were eventually removed using equipment more powerful than the usual spanners - additionally, although large amounts of underseal mastic had been applied to all rust-prone areas of the car, some of the tubing showed signs of  rust.
It was decided that it was unsafe to re-use any of the original hydraulic tubing and that copper piping would be used instead.  After the tubing at the front of the car had been removed and equivalent length replacements, complete with the appropriate new unions, had been obtained, it was found that the unions would not screw into the slave cylinders, etc.  This was an easy mistake to make as visual comparison of the old and new unions did not indicate that they were different - unions with the correct threads have now been fitted.
It was not a surprise to see that the rubber/metal bushes on the steering centre arm had deteriorated and were not up to the MOT, or our, standards of safety and reliability.  The car reputedly has a Standard 10 steering box and other steering components except for the idler arm bracket that is an in-house Fairthorpe product.  As no information on sources of replacement bushes resulted from my posting on the FSCC website message board, I posted a request in the Standard Motor Club for information.
The result was the name of a company in Tamworth, Staffordshire that makes replacement bush/pin units that do not use rubber and so have a likely longer life.  Not only that, but the informant is local to me and has offered facilities for pressing the new bushes into the centre bar!  That's one problem resolved.