Housing Terraces in Wales : a minor addressing conundrum

Two terraces of housing off the Holyhead Road (former A5) in Llanfair PG.
Penucheldre and (to the right Britannia) Terrrace. A typical type of housing throughout Wales, they provoke some addressing conundrums.

In May 2015 I attended the funeral of a relative in the Anglesey village of Llanfairpwllgywngyll (usually referred to as Llanfairpwll or Llanfair PG, but perhaps better known for having an extremely silly long form of the name). This is the ancestral village of my maternal great-grandfather: the funeral marked the end of around 150 years of members of the family living in the same house that he grew up in.

I know the house well. As a small child I visited frequently. It was only a short excursion by bus from Bangor, where we lived. My mother knew it much better: in the early part of WWII she and her grandmother lived here with my great-grandfather's sister. Even when I was small the village was not very large. When my mother was a girl there was much open land between the old part of the village (Pentre Uchaf) and the newer part (Pentre Isaf) next to the railway and main road to Holyhead. By the late 1970s the village had grown immeasurably with lots of overspill suburban housing for Bangor.

The big change between 1939 and the end of the '70s was that streets started to be named and houses numbered along the street. Prior to that building development had been piecemeal: most usually a mix of individual houses and most typical of many parts of Wales: named terraces. By this I mean short terraces of houses where the terrace rather than the closest street provides the name used in the address. Elsewhere there are plenty of terraced houses where individual terraces have names (often shown on a carved stone set into the brickwork of the terrace), but the numbering of houses solely relates to the street.