Just to update you, I've been searching through all of my resources since reading your post the day after you posted, but unfortunately I had initially been unable to match this property exactly to any of the known structures contained within my archives although I do have my suspicion about one particular construction type, which I shall reveal at the end this post.
I had suspected that this property was more likely to be an unrecorded variant of one of the main system build manufacturers, as certain companies frequently experimented with different layouts, window placements, roofing materials and exterior surface compositions, which drastically changed the external appearance of the property, when compared to their standard more well know examples.
If I were make an educated guess here, based upon the research that I have already conducted, I would suggest that this could well be a Arrowhead House, manufactured by Rigid Frame Construction Ltd between 1963-70.
Arrowheads were produced in a wide range of designs, often using equally varied materials for external wall cladding which also included vertical tile hanging to the gable (end) wall which we see in your example.
Arrowhead properties are of steel frame construction with the typical shallow pitched roofs that you mentioned above..
I have attached several images of a variety of Arrowhead designs below, just to give you an idea of the range and scope of their designs.
May I ask if you are aware of any more similar buildings on the estate or near to the location?
I've already had a quick scout round the area on Google StreetView, but so far I haven't seen anything similar.
Here's a closer look at Arrrowhead properties in Newland Way, Monmouth that appear to be the most visually similar to your subject property, especially the deep Fascia panel below the roofline and the unusually shaped 1st floor narrow windows.