AirHint found the following cheapest return flights from London (LCY) to Seoul (ICN) in September 2025 (see full year).

Return flights

16 Sep - 15 Oct	SWISS
29 Sep - 20 Oct	KLM
30 Sep - 26 Oct	KLM
29 Sep - 12 Oct	KLM
22 Sep - 08 Oct	KLM
01 Sep - 09 Oct	KLM
30 Sep - 12 Oct	KLM
29 Sep - 14 Oct	KLM
23 Sep - 07 Oct	KLM
30 Sep - 21 Oct	KLM
02 Sep - 17 Sep	SWISS
04 Sep - 17 Sep	KLM
11 Sep - 14 Sep	KLM
01 Sep - 16 Sep	KLM
10 Sep - 16 Sep	KLM
01 Sep - 14 Sep	KLM
09 Sep - 23 Sep	KLM
10 Sep - 17 Sep	British Airways
08 Sep - 17 Sep	KLM
01 Sep - 17 Sep	KLM

Also check the deals for one-way flights from London to Seoul in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from London to Seoul in September from 654€

Return flights