The manchester encoding library from mchr3k worked great, and I quickly made a reliable connection between the Tiny and the Uno.
I was worried about RF interference from running the Scalextric car, so I left the transmitter by the track and ran the car round. That seemed to make no noticeable difference to the signal quality, so I’m happy that I’ll be able to get data back, and at a pretty reasonable data rate.
Next up was adding a header to the Accelerometer board and giving it a go. The setup for the accelerometer is very simple, 1.8 – 3.6V in and analog outputs for the X Y Z readings. I got the Uno hooked up and used the inbuilt ADC to read the pins – and it worked first time.
Finally, I wanted to get it going with the Tiny. Only minor problem here is that I’m powering the Tiny with a 4.5V battery pack. I’m planning to get this working from coin batteries eventually, but I haven’t bought them or the clips yet. So I just used a simple voltage divider (two 5.1K resistors I had about) to give a sensible voltage for the accelerometer for testing.
With that all wired up, I could transmit the three readings using the ADC on the Tiny to the Uno! Only problem I have at the moment is the Uno can’t tell which reading is which, so if a single reading is lost the axes all rotate one place 
I’ll post the code once I’ve added some markers to fix that up.