Most seem to be north east. Below are what I've seen reported (some of these may be duplicate reports - I'm cutting and pasting from various web sites):
Filey: 40 Red Veined Darters all males bar 3- 4 females seen in tandem and ovipositing
12th June, Burton Riggs NR near Scarborough: 20 male Red-veined Darters
13th June, Reighton (between Filey and Flamborough): 2 Red-veined Darters
19 at "a site in North Yorkshire",
3 in "West Yorkshire"
2 "in Worcestershire"
10+ at Burton Riggs NR near Scarborough
5+ at Speeton Ponds near Flamborough
2 at South Gare near Redcar
S. Devon (1 probable),
Co. Durham
" at least 4 sites in Yorkshire"
Up to 15 at Belvide Reservoir, Staffs
Pennington Flash Country Park, Leigh, Lancs SJ636993.
5 at Holme Dunes, Norfolk
2 at Kelling water meadows, Norfolk
Hatchet Pond in the New Forest
Lesser Emperor also recorded
"near Scarborough on 12/6."
Haddiscoe New Cut Norfolk grid ref 435447
Little Bradleys Ponds, Devon
Exminster Marshes,Devon
Burton Riggs NR near Scarborough
Cotswold Water Park , wiltshire