Look for a shot of a MK1 front on and you will work out where the factory spot was pretty easily

From what I understand (don't take this as gospel), if you wanted to have a cage fitted, your car would become a Modified Vehicle, and require an engineering certificate on top of the RWC, under the revised permit rules. 
 
My 2c worth is that there is a staggered Engineering Certificate system required for permit driven cars.  This would allow modications at different levels not a one size fits all approach.  ie your CAMS approved cage should only require say a level 1 inspection if the driveline is factory correct.  A car with a V8 conversion brake swap revised suspension etc would be say a level 5.  You get the idea 

what?
From my discussions a 6 point cage is not a problem so long as the front legs go through the dash.

Exactly my point. From the cars I see on club reg, this is definately the minority, either meaning they were previously signed off without a valid rwc or they have VASS approval? I'm guessing more than likely it was the former.
 
Unfortunately, (or fortunately) there aren't too many standard escorts around these days with factory issued drivelines and braking systems
 
Shaun

Thanks Gareth.

That is what I had explained to me by the rwc inspector???
For rwc had to meet VS128, and for that it must go through the dash.
I guess it depends on who you speak to, ultimately it's their call and their rwc license.