has this tree been in a very shady spot? Its difficult to decide what it is, it might be one of the purple leaved palmatum types, but just hasn't had enough sun, or its suffered a bit of drought here and there and the leaves are changing colour before they fall.

Thanks for your reply. It's been in a partly shady spot recently, but has been in different positions and has always been this blend of colours. Before the leaves fall they go a mixture of oranges and reds.

In that case, its impossible to identify it - it's clearly an Acer palmatum variety, not a dissectum, so all I can do is guess that it will likely not get over 10 feet, and maybe not taller than 8 feet, but it will spread around 4- 6 feet eventually.