RISC OSMap of G.W. SignalboxesRISC OS
http://www.svrsig.org/gwmap/GWMap.htm
Sxxxx numberSignal Box nameView on map squareOther information including SRS diagram number
  Dousland Map BH18
SX536688
SRS diagram D1 (old and new boxes)
  Princetown Map BJ20
SX587735
SRS diagram W25/23
Prices are shown here.