4lb lump hammer and a bit of brute force sorted the problem. Was a bit of a pig to get the ball joint out of the hub too and it done this to my ball joint splitter:
Then on putting the new one in and it being very tight I got a bit creative with the jack and the driveshaft came out resulting in losing a litre or more of relatively new gear oil
After eventually lining the ball joint up with the hub and jacking the car up by the ball joint, then also using a chisel to open up where the ball joint fits in it seemed to be going nowhere, until a two footed kick/push with the soles of my trainers on the brake disc was just enough to get the ball joint into the hub.
Once I get it through it's MOT I might do the otherside, at least I'll be prepared now.