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
  Basingstoke (G.W.) Map DK38
SU641527
SRS diagram B289
  Litchfield Map DF39
SU460538
SRS diagram D84 (old and new boxes)
  Sherfield Map DK39
SU658560
SRS diagram S138
Prices are shown here.