I presume they have to be under 19 on the 1st of January. Davenport is only 17 and I'm pretty sure I'm safe in saying that England try to pick only players who are just under the maximum age so it would only be 18/19 year olds for the U19's (presuming they turned 19 since the 1st of Jan).
Edit: that would apply to Patching too.
They have to be born before 1/1/97