SELECT node.*
        FROM gps_nodes as node,
     (SELECT count(*) as n, g.gid  FROM linestrings as l , gps_nodes as g
          WHERE ST_equals(l.geom_line, ST_GeomFromText('LINESTRING(g.EASTING g.NORTHING, -1.911782 53.26144)') GROUB BY g.gid)
 as c
        WHERE node.gid = c.gid AND c.n = 0 

(i didnt test, may not contains necessary amount of ) )

query creates "table" which has n and gid columns ( n is count and gid is unique id in gps_table) , assigns alias c for it and then joins table with gps_nodes table ( alias node) and limits rows to where n = 0

change gid to match your gps_nodes table. note table alias use

 SELECT node.*
        FROM gps_nodes as node,
     (SELECT count(*) as n, g.gid  FROM linestrings as l , gps_nodes as g
          WHERE ST_equals(l.geom_line, ST_GeomFromText('LINESTRING(g.EASTING g.NORTHING, -1.911782 53.26144)')) GROUP BY g.gid)
 as c
        WHERE node.gid = c.gid AND c.n = 0 

(i didnt test, may not contains necessary amount of ) )

query creates "table" which has n and gid columns ( n is count and gid is unique id in gps_table) , assigns alias c for it and then joins table with gps_nodes table ( alias node) and limits rows to where n = 0

change gid to match your gps_nodes table. note table alias use