Question
I have a Deshojo maple bonsai that I purchased 2 months ago from a Bonsai dealer in the UK. I believe that it was grown in Japan but not 100% sure on that. I have done so early pruning and the tree seems to be growning very well, sprouting a few new shoots. I read that in order to get a good set of bright red Autumn leaves I should cut off ALL the green ones! It says that the timing of this is very important as it must not be too early that the buds have not developed and not to late that new buds will not have time to form ready for next year.

Considering the UK climate, what time of the year should I remove the present leave? or as I have just purchased it should I not bother to do it this season?

I believe the tree is about 3 years only and stands about 30cm high.

Thank you for your help  

Answer
As you just have bought the tree, maybe it would be a good idea to leave it alone for now.
What makes the leaves to turn red or orange, are certain substances that change color according to the amount of light (and the intensity of it) received. Also the amount of water would have an influence on it.
Pruning the green leaves would help it stethically but not that it would help the plant to make more red leaves.
Pruning in any case, would stimulate certain responses from trees. You wouldn't want to have your tree putting out new shoots in september. This could happen if after pruning you had some warm weather again in the fall.
In any case you always have to experiment with it.
The Japanese have a saying: "Narau yori wa nareru"
which could be translated as: Better than studing, get accostumed with it.
Good luck, and keep in touch!