Note there are two roads one above the other in this street caled Saxon Avenue

That's how it is. Your system keeps dropping one of them. If you delete the road it means it's not navigable since the house numbers don't tally with the street. Odd numbers are accessed on the bottom road, even numbers top road. Middle is a footpath. It's quite easy, really. During building of the estate, cars are parked on the centre footpath. That's not the road. Modern planning.