My 20vt has done 56k and is lowered on Eibachs. When on undulating roads it's very bouncy. Are the dampers likely worn ? What's the best way to test them ? Thanks.

Yes.

Eibach springs are uprated so will exaggerate the bouncing of a tired damper.
Ideally you'd want a slightly uprated damper to match the damping rates of the spring.
Bilstein now offer a valving service so they will build you a bespoke damper to match the Eibachs.

PM balancemotouk. He owns Balance Motorsport, knows a lot about dampers and I'm sure he'll do a deal for a fellow coupe owner.

You can also replace with Munroe OEM dampers, although the Eibachs are probably better suited to the Bilsteins. Alternative Autos are worth a call as well as Balance as said above.

Either way you'll have a noticeable improvement in ride when changing old to new.

I put Monroe's all round and I am pleased with the ride and handling, Rog has just replaced the front arms, drop links, track rods etc and the car feels so so much better; very pleased. Along with new discs and pads.

Monroe + Eibach are fine though one of my front dampers gave up the ghosts within 1st month of use. I heard a lot of complaints about Monroe dampers.