For those who are interested, the ring network I'm using is described here:

http://www.wintergroundfairlands.com/2012/12/daisy-chaining-serial-connections.html

However, I've completely ignored something quite important!

In my model so far, the stations at the end of the single track section have seemingly endless capacity, when a train leaves the section and enters the station the last signal remains green... Not very good if your station has three tracks, one of which contains a train going the other way, and you send four trains down to it...

Even worse, the points at the station aren't neccesarily going to be straight so the last signal might need to display some kind of "slow" aspect....

I think a I might need to get my thinking cap on again....

On a happier note, my Arduino experiment box arrived today. £20 (or so), it includes an Arduino, switches, LED's, breadboards, servo, stepper motor, all sorts... Good value, given an Arduino is £25 (or so) at Maplins...