My Feltham Earlies were germinated (about 70%) outside during that warm spell we had in March Steve. It looks like summer is now over but they are still out, in cells, and nearly big enough to plant out. But then - I'm balmy.

I have mine in a coldframe along with a lot of other veg seedlings. My plan is to leave them there for another week, so end April. If you have a plunge bed then you could put yours there Steve?

I will sow ours directly into the ground in early May.

Just noticed you are in West Yorks, I would wait till mid May as Bulbaholic has said. I live near the sea, so it is that bit milder and tend to avoid hard frosts, though pots had some frozen soil last week! Last year it was frost free from April till November here.