"the Service Manager had attempted to get a replacement windscreen ordered in from MG, last week, but they apparently wouldn't provide one 'preemptively', only if it was needed"
That in a nutshell sums up MG UK and that is why it's destined to remain a budget brand.
Service manager at the garage trying to do the sensible right thing and get a new windscreen in, just in case required.
MG, like the breather mod refusing unless it's actually required. Would probably want photos to prove the window wasn't usable/damage.
The decent garages are so up against it, fortunately they were able to reuse it.