  We study the reaction-diffusion process $A+B\to \emptyset$ with injection of
each species at opposite boundaries of a one-dimensional lattice and bulk
driving of each species in opposing directions with a hardcore interaction. The
system shows the novel feature of phase transitions between localised and
delocalised reaction zones as the injection rate or reaction rate is varied. An
approximate analytical form for the phase diagram is derived by relating both
the domain of reactants $A$ and the domain of reactants $B$ to asymmetric
exclusion processes with open boundaries, a system for which the phase diagram
is known exactly, giving rise to three phases. The reaction zone width $w$ is
described by a finite size scaling form relating the early time growth,
relaxation time and saturation width exponents. In each phase the exponents are
distinct from the previously studied case where the reactants diffuse
isotropically.
