Caporegime
I think it's been too cold for grass seed to grow until the last few days. And as well as being too cold, it's been really dry as well.
The areas I've really needed to get going (where I've cut plants away and wanted to reseed an area of lawn) I've had covered with some spare corrugated clear roofing I had lying around. The grass underneath that started growing within a week, and the grass not covered still hasn't started to grow. Also stopped birds getting at the seed.
That's an idea to be fair, shame I don't have any.
I'm going to try vigorously watering it, otherwise I'll throw more seed in the parts I'm not digging up in a month or two.