124 E300D stumbling after start up

[Chazchuzzlewitt]

After sorting my glow-plug light issue (bad connector) I still have a problem- this might just be down to cold weather, but my 606-powered 124 will start to stumble a bit after the first cold start of the day. It starts fine, but after about 2-3 secs running sounds like it's mis-firing with the revs going up and down until I give it a bit of gas, then it smooths out after a few more seconds.

I recently changed 4 of the 6 glow plugs, which seemed to cure the bad 'chugging' I had on start-up before when moving off.