Hi Phil,
You could be right there, the rubber is definitely perished. I will try what Chuff is recommending and see if we can work out what is going on.  I have also now ordered a new shifter from Rix Engineering so hopefully one way or the other I can get it sorted.
Once again, I thank everyone for their invaluable help. 

Hi Guys,
I received my RIX Engineering shift lever today and it looks to be excellent quality as I’d hoped. When I compared it with the original, the measurement down to where the forks sit over the “saddle” on the shift shaft was approx 4mm shorter so I it seems that maybe my original shifter had either worn in the nylon “ball joint” or as Phil indicated the rubber “spring” had perished and gone hard, and was allowing the shifter to sit lower than it should.

I remover the original gearbox adaptor and fitted the new RIX shift lever and everything feels great. Reverse is locked out like it should be and is easily found when the shift lever is pressed down. I haven’t driven the car yet but the shift action in gears 1,2,3 and 4 feels short and crisp. Hopefully this feels the same when I drive the car tomorrow.

I’d just like to thank everyone once again for their help. The knowledge and assistance offered by members of this forum is much appreciated and it’s great to share a common interest with such great people.

Flighter
There's a 'saddle clip' in the gearbox that locks out reverse. They are made of plastic and eventually break, allowing reverse to be selected without depressing the lever. Replacing it may be all you need to solve that problem. You can pull them out from the shifter hole with a pair of needle nose pliers. Replacements are available on eBay (Au and UK) either out of:
 
plastic (cheapest and stock):
https://www.ebay.com.au/itm/FORD-ESCORT-E-GEARBOX-RAIL-CLIP-SADDLE-PAIR-SET-OF-2-2PCS-2738/132497668879?epid=1748346018&hash=item1ed979fb0f%3Ag%3AtAMAAOSwnMRZ3%7EWR&_sacat=0&_nkw=escort+saddle+gearbox&_from=R40&rt=nc&_trksid=m570.l1313
Watch out for moulding flashing on these ones - compare photos and your existing clip before pushing the new one in,
 
and glass filled nylon (stronger than plastic, more expensive, but probably a better option).
https://www.ebay.com.au/itm/FORD-TYPE-9-GEARBOX-ESCORT-CORTINA-CAPRI-SIERRA-H-DUTY-GEAR-LEVER-SADDLE-CLIP/152748287665?hash=item239081e6b1%3Ag%3AbQ0AAOSwuOxZvExe&_sacat=0&_nkw=escort+saddle+gearbox&_from=R40&rt=nc&_trksid=m570.l1313
 
I've seen metal ones too, but none presently listed on eBay that I can see.
 
You can buy short throw shifters brand new from the usual suspects too, e.g. motorsport-tools, eBay UK.
https://www.motorsport-tools.com/mk2-escort-h-duty-4-speed-rocket-gear-lever-quik-shift.html
 

hi flighter, the saddle you add here looks different to the one in my box, mine looks to be a smooth white roundish or are these supposed to sit on top of the white thing? the one i have looks like this 
 
should the ones you shown sit on top of the white ones? cheers

Hi Griezy. I've never seen a clip like that before because I've only ever used Type E gearboxes fitted to Aus Escorts, or Type 9 five speed gearboxes that conveniently bolt up to Escort bellhousings. That clip is for a Type 2 or 3 gearbox, which I have no experience with.