"Woman front bits" meaning

Solution 1:

In the UK, certainly, a fanny is slang for vagina.

A lady's front bits would definitely mean vagina and not breasts. A less-oft-used term is "front bum" which is also slang for vagina.

I have never known front bits refer to breasts.

Solution 2:

In British English fanny means a woman's genitals, and the NOAD adds also that it means a person's buttocks. Actually, the NOAD reports first "a person's buttocks," and then the British meaning.

The Shorter Oxford English Dictionary says that bits means a person's genitals, or a woman's breasts. The same dictionary says that fanny means the female genitals, or the buttocks (in North American); it also adds the word can be used in combination with other words, such as in fanny belt, or fanny pack.