  It has become increasingly clear that a full understanding of the physics of
electrons in disordered systems requires an approach in which both disorder and
interactions are taken into account. Work on small numbers of electrons has
suggested that interactions can substantially increase the localisation length
in 1 dimensional systems and possibly lead to delocalisation in 2D. It has not
been clear, however, to what extent these results are applicable to systems
with a finite density of electrons. Among numerical approaches the transfer
matrix method combined with finite size scaling has been particularly
successful for non--interacting systems, whereas the density matrix
renormalisation group successfully describes interacting systems. We have
developed a new approach which combines elements of both these methods and have
successfully applied it to spinless electrons with nearest neighbour
interactions.
