This is a graft hybrid between Laburnum and Chamaecytisus purpurea. The correct name for this type of graft is a chimera. Sometimes the chimera breaks down and you get true growths of the Laburnum with yellow flowers and the purple flowers of the Chamaecytisus. This is supposed to be the reason for growing it.

So far the tree has produced uniform blooms of a peach/gold colour like in my avatar pic, I wonder if I pruned this broom growth off I could grow it on?

If you took cuttings of the Chamaecytisus part then you would indeed get a chamaecytisus. Ditto Laburnum. Not sure about the success rate with cuttings for either of these, never tried. Don't like Laburnum and the other is too tender for us here. They do not survive our winter.