I assume that it's a 16v engine if it's a mk2? If so, then it'll be tricky because the plugs will be quite far down between the cams. I've seen it happen on an 8v Ka before.
The plugs had snapped in half. We had to pour boiling water over the plugs and then cold water to try and contract them a bit. Then we hammered a screwdriver into what was left of the plug and were able to get them out - only just though.
I assume that they're planning on removing the head before they start drilling the stuck plug out? If not, they might get a lot of swarf into the engine.
Installing them with a bit of copper grease can help things when it comes to removal time.