From the jaycar website - To fit PCB (mm) Horizontal 62 x 49
I had designed the board based on a 100 x 50 size for no particular reason other than that was one of the sizes available from iteadstudio.com
I could try to fit it on a 62 x 49 size board - I need to learn how to design my own parts as the RTC module I had used is not actually the correct size.
As for an LCD, buttons etc - no, there is no plan for these. The original idea from
@Sam Parker was for a small, low cost solution - adding these additional components adds to the cost and complexity. The downside is that the variables need to be hard coded using the Arduino IDE (software). Given that this would hopefully be a 'set and forget' solution this was not considered to be a major problem.
Longer term, I would love to be able to add in a Bluetooth module (around $5) and use a mobile device to program the Arduino - this will happen, but it's not on the short term radar (although I have managed to learn enough about Eagle to create a usable board in a week or two :D)