It seems to me it depends on what your neighbour got for 2500 (and possibly how well they know the installer). If itís that price for the stove (with back boiler), installation and/or pipes, tank(s), pump etc. then it may not be so expensive to your comparison of £700, if just for the stove and back boiler, would not be like for like. Iíve never seen an open fire here with a back boiler, a glass enclosed unit i.e. thermocamino yes, but not an open system. When you say not efficient, in what way?