Very thin and patchy hedge

[Brownowlahi]

Hi, at the top of the garden we had a fence, with about 8 foot of waste land behind it, then a boundary hedge. We have removed the fence and are trying to sort out the land behind it as it is quite a big bit of land. The only thing is the hedge, which we think is a hawthorn is in quite a bad way and seems to be really patchy with loads of gaps in. I'm at a loss to know what to do with it. Chop it all down and start again with something different (but how long would that take to establish?). Try to fill in the gaps with something else and hope it takes and fills the gaps effectively. Or someone suggested we might be able to get it layed, does anyone know how much that might cost to do? Or any other ideas would be really welcome. Dh has even less idea and thinks it will just thicken by itself (I have no idea how when there are no branches/twigs/shoots anywhere near the hole!
Thanks in advance.

Is it a gappy bottom, or all over? If all over, then cutting it hard back on one side, then feeding and mulching will encourage that side to sprout lots of new growth. The following year, do the same to the other side.
if is a gappy bottom, make sure that the top of the hedge is narrower than the bottom (ie trim it so it is). And keep the bottom of the hedge free of weeds. It MIGHT then thicken up at the bottom too. I have a gappy bottom and this didn't work for me though :-(.

The hedge's bottom I mean, not mine....!