First I painted the track-bed grey with a couple of tester pots from the DIY store (allowing for future track). The track was stuck down with No More Nails (I thought it might be stronger than PVA but it didn't dry clear, PVA would have been better) and pinned, althoug the track pins were reluctant to go through the ply! At the board edges I used a short length of nickel-silver flexi-track, where the rails crossed the joint I put in brass screws both sides, and then soldered the rails to them, then cut the rails. This should make the track robust at the edge and ensure precise alignment, even though it is cosmetically lacking! Each rail then had a wire soldered to it, running over the hinge post to the rail on the other side, ensuring electrical continuity. The photos should make this clear.
The Hornby controller was screwed to the board in one corner and connected up. In the siding I added a re-railer ramp with uncoupler, I'm surprised Hornby don't include these in the train set. I know they are not pretty but for a child they are very useful! A set of Hornby platforms were cut to fit the board joint and the length of the straight and stuck down with a glue gun. I used the small station building as although I have the larger one, it fouls the other end of the platform when the board is folded! I also found a signal box, this and the station came from my parent's loft ... Finally more tester-pots were used to paint the rest of the board a rather un-convincing grass green, I threw some handfuls of scatter onto the wet paint too. Frankly it hasn't worked that well but it is better than bare ply, and this is just a train set! It can all be spruced up over time.
The real test came today, my Son's 4th Birthday. Even with lots of other presents including Playmobil (which needed a surprising amount of assembly!) and Firman Sam toys (which he is mad about), he was really excited when he opened the big parcel of the train set! Then I produced the board and he set to playing trains. In fact I have spent a significant part of the day kneeling on the floor playing with him - apparently I am the Fat Controller! Clearly it has been a big hit.
So does the board work? Well yes, although I really should get some handles to make moving it about easier. As you can see though - it does fit under the bed as intended! It is really easy to unfold and plug the controller in, so can be up and running in a couple of minutes, so mission accomplished!