Barnaby,
If you do go the Sig-na Track route I would love to read your thoughts on the system. I ran across its website a couple of years ago and have to say it is intriguing. Even though I am firmly with MRC (Gaugemaster) Prodigy Express/Advance, I always enjoy hearing about other systems should I decide to "expand my horizons" (yes, I'm an HO guy . . . . . well, let's play a bit with OO, ok, I'm a HO and OO guy ONLY. . . .wait a minute this 7mm British O looks interesting . . you get the picture).