My CU has no spare ways, but I'm putting in an electric shower. I
happened to have one of these lying about:
http://www.screwfix.com/app/sfd/cat/...99711&id=90026
It was going cheap at B&Q a few months ago.

Can this be installed alongside the existing CU to provide for the
shower circuit? If so how are the connections made to "piggy back" it?
The cable to the 9.5kw shower (which is only about two metres from the
CU) is 10mm stuff but this is a 63A unit, so surely it needs some
further protection in the form of an MCB?

I think it's time to call out an electrician, but I'd like to know
what's what before I do.