Just 13 ! unlucky for some!
In Uk :-
Barn Owl easiest places North Norfolk like off Lady Anne's Drive near Wells, or Warham's Green, north lincs coast like just inland of donna nook, and any local spot where you know they are. Also seen dark-breasted birds.
Short-Eared Owl again easy in winter at places like Gayton Sands, dee estuary, or on many moorland areas with effort.
Long-Eared Owl more localised but with effort & a little knowledge quite easy at Park Hall CP, Stoke, or Cannock Chase.
Tawny Owl commonest but hardest. Cheshire countryside can be easiest I have found, on roads approaching Audlem for example.
Little Owl used to be regular at Belvide Res, found them too on lower approaches to North Staffs Moors.
Scop's Owl saw bird in tree and in flight in Oxfordshire a couple of years back. Mediocre views though.
Snowy Owl oil-stained ship assisted immature male seen on ground at Trimley Marshes, felixstowe. Gorgeous immature female seen up on North Cornwall moors this year. Not seen one in flight though.
Eagle Owl 2 adults and 3 wild-born juveniles seen on North Lancs Moors near Dunsop Bridge. Very close encounter with angry female.
ABROAD
Great Horned Owl saw family of 4 in trees approaching Reifel Bird Sanctuary, near Vancouver, Canada several years ago.
Great Grey Owl magnificent adult female seen superbly on nest near Oulu, Finland this year.
Pygmy Owl adult male seen on top of pine at same location as above - Oulu area,
Tengmalm's Owl female popped head & shoulders out of nest box at Oulu.
Ural Owl glimpsed adult female through slot in nestbox at Oulu. Could i/d bird from views but very restricted view.