Green’s Dictionary of Slang

1. one who is partially bald.

1984

Partridge DSUE (8th edn) 38/2: C.20.

2. the head.

2001

(con. late 1940s) V. Foot Sixteen Shillings And Tuppence Ha’penny 30: I can’t tell yer everything Esmerelda – only what me brain in me bacon bonce knows.

3. (UK juv.) the face.

1959

I. & P. Opie Lore and Lang. of Schoolchildren (1977) 188: The unfortunate fat boy [...] whose ‘bacon bonce’ (face) is flanked with ‘slobber chops’.

4. a dullard, a simpleton, a yokel.

1958		Daily Tel. 4 June in DSUE (1984).
1980		Barltrop & Wolveridge Muvver Tongue 91: A slow or absent-minded person [...] can be called ‘bacon-bonce’.