Cheers guys. Mucho helpfullo.
It's uneven because some bone ed has laid it badly and then planed and hacked at it. Looks more like he's used an adze in places. Because he has used the wrong bonding most of it has come loose. So I am taking it up where it's loose, cleaning the concrete and bitumen form the pieces of parkey and relaying it.
It is taking aaaaaaages.
Still! it will look nice when finished.