Thanks for your reply Jack. I have it blinking on the board in front of me now!
Your suggestion to focus on the crystal and the capacitors turned out to be correct, and the answer was in the capacitors I was using.
I didn't realise the capacitor choice was so sensitive - the original capacitors (in the photo) are small blue ones with just '.1' printed on them. I has also tried other ones with '221' on them. After reading your post I also tried another set with '220' on them - none of these worked.
Finally the ones that work have '22' (underlined) on them. A photo of them all, including the correct ones on the right is attached.
Again, thanks for the suggestion.
