OK, some better news guys..
earlier I phoned the Insurance company`s "unhelpful" lines to be put through to the accredited glass replacement company.
explained my thoughts to the very helpful guy who talked me through things...
Now, reading through my online Insurance details and straight talking to the acredited glass replacement company showed most of you were correct in saying £75 is required at point of fitting, and my full NCB "should" be retained BUT held for 1 year in a bond if you like, to see if any more claims have to be made...
just hope my insurer sees it that way
So, yes, thanks for your imput on this, and it must be said,
it did make me feel better about phoning through.
a second hand screen would have come pre stressed by years of weathers and use anyway, let alone the price.
just waiting for the golden eagle to drop some ££`s into my pension pot.....lol