From Airline Route:The following is overall Wizz Air UK A321 operation in winter 2019/20 season, as of 06SEP19:
London Luton – Athens 5 weekly (7 weekly 10DEC19 – 14JAN20)
London Luton – Belgrade 3 weekly (4 weekly 11DEC19 – 17JAN20)
London Luton – Bergen 3 weekly (4 weekly 09DEC19 – 13JAN20)
London Luton – Bourgas 2 weekly
London Luton – Bratislava 4 weekly (5 weekly 11DEC19 – 12JAN20)
London Luton – Constanta 2 weekly (3 weekly 12DEC19 – 14JAN20)
London Luton – Grenoble 2 weekly (From 14DEC19)
London Luton – Kaunas 5 weekly (6 weekly 14DEC19 – 13JAN20)
London Luton – Kosice 5 weekly (7 weekly 13DEC19 – 14JAN20)
London Luton – Larnaca 7 weekly (8-9 weekly from 01JAN20)
London Luton – Lisbon 5 weekly (7 weekly 09DEC19 – 13JAN20)
London Luton – Lublin 4 weekly (8 weekly 11DEC19 – 15JAN20, 5 weekly from 16JAN20)
London Luton – Moscow Vnukovo 1 daily
London Luton – Oslo 5 weekly (7 weekly 11DEC19 – 13JAN20)
London Luton – Palanga 2 weekly (3 weekly 12DEC19 – 14JAN20)
London Luton – Poprad/Tatry 2 weekly
London Luton – Porto 1 weekly (02NOV19 – 07DEC19)
London Luton – Poznan 6 weekly (7 weekly 09DEC19 – 12JAN20)
London Luton – Prague 3 weekly (29OCT19 – 07DEC19)
London Luton – Pristina 1 weekly (01NOV19 – 06DEC19)
London Luton – Reykjavik Keflavik 4 weekly (5 weekly 15DEC19 – 09JAN20)
London Luton – St. Petersburg 7 weekly
London Luton – Stavanger 2 weekly (3 weekly 12DEC19 – 14JAN20)
London Luton – Suceava 1 weekly (until 12JAN20)
London Luton – Szczytno 1 weekly (2 weekly from 13DEC19)
London Luton – Thessaloniki 2 weekly
London Luton – Tirana 5 weekly (7 weekly 11DEC19 – 11JAN20)
London Luton – Tromso 2 weekly (from 09DEC19)
Note - these are W9 only. Does not include W6.
I don't think I've seen mention of Szczytno before.