You
can break your journey
unless it is made "
clear in [FCCs] notices and other publications" (source: NRCoC) so, do they make it clear that you can't? If not, then you can!
The only regular ticket type where such a prohibition is made clear is with an Advance ticket.
Not only that, but there only used to be provision to bar break of journey on the
outward portion of
non-Day tickets, it is only since "simplification" in 2008 that things have been made more complicated. However I was assured by someone senior at ATOC that Simplification was not about eroding our rights, therefore there should be no attempts to restrict break of journey to either Day tickets or outward portions.
The easiest way to check for a BOJ restriction is to check the unofficial brfares.com site, though this is arguably not binding anyway. In this case, for a PBO - KGX '
CBA', restriction FB, there is no such prohibition.
Apparently the DfT and TOCs are plotting to get rid of these tickets, and make us all use smart cards and pay the inter-available 'Off Peak' price! :-x