French Marigolds are not hardy and I would not start to germinate their seeds for another month at least. They are quick to germinate and they take 6-8 weeks to flower and we potentially have frost till May, so you should avoid planting out till then ideally.

If you propagate them now then keep them in it (unheated) until they are 4 inches or so tall/have a few proper leaves, then gradually put them in a cold frame or outside when during the day and bring them in during the night to harden them off. I have put them out in April but I have a south facing garden and near the coast and they did OK.

Thankyou

Hi Cox, I,m in the English midlands and if I leave sowing until mid march I don't need the propagator, they are then ready to harden off to go out in late may, any earlier they get leggy but its still too risky to plant them out
You are on the gulf stream up there but snow on the beach in the Machars in Galloway for the past few years makes me wonder if you may get late frosts too

thanks