Hi Ed,
Brown Hawkers occur in a variety of habitats,from woodland ponds which are not too enclosed with foliage to reedy ditches and so is a fairly cosmopolitan breeding species wherever there is still,standing water.When maturing,they,as a lot of other species use woodland to hunt and rest up and at these times can be found well away from water.They also occur as migrants from the near continent,so this might also explain your sightings and would tie in with,what seems to be a very good year so far for Odonata migration.Just keep checking those Migrant Hawkers!
.Regards
Steve