[abirkill]

Not all houses in the UK have numbers, especially in rural areas. If you don't live in a village or larger, it's pretty common to have a house name, and no number. (Edit: I just checked the village I grew up in, and was surprised to find that out of 48 houses covered by the postcode, 41 of them only have a house name, no number -- I'd have guessed closer to a 50/50 ratio).

Even in cities, it's not particularly unusual to have houses that don't have numbers, especially older houses -- in my parents' postcode, two of the houses only have a name.

House names are fully supported by correctly implemented postcode lookup systems -- for example, in the common online use-case where you enter your postcode and a list of houses is brought up, the list will include the houses that only have name identifiers.