After replacing the split EGR/Intercooler hose, it seems to have fixed the problem. Still plenty of smoke when accelerating hard but I imagine the exhaust must be full of unburnt fuel & a long journey should sort it.
Surging & continual smoke has gone anyway. Power restored & having a clean EGR valve should improve fuel economy. I'll update when I know more.
It was a bit tricky to remove the bottom hose jubilee clip without having a ramp, but using a 7mm socket on the clip sorted it. I removed the EGR valve to give me more room to work. Took about 75 mins in all.
Thanks to all that helped with this.