So, for a while now i've been having an intermittent issue where the engine will start for a few seconds then cut out and require extensive 'cranking' to restart. Only code that burps up is p0089. It's gone from a 'once every couple of months issue' to a couple of times a week. So after doing the basic checks of checking tank sender for obstructions and damage to pipework I am looking at doing a 'leak off test' to check injectors.

So, if I have a faulty injector what is the procedure to change it. Can I replace one injector or does it have to be a set? Do they have to come from Ford only? Do the injectors require 'coding' and will my Forscan be capable of doing it?

I'm not getting any nibbles, how about has anyone ever changed a diesel injector on a 1.8tdci?

You can replace injectors singly, but at this age, chances are if one is duff, others will be as well.  It doesn't sound like an injector fault though, more likely to be the fuel pressure regulator or even the HP pump imo.