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

Return flights

28 Sep - 02 Oct	British Airways	direct
21 Sep - 25 Sep	British Airways
21 Sep - 25 Sep	British Airways	direct
25 Sep - 02 Oct	British Airways
06 Sep - 10 Sep	ITA Airways
26 Sep - 30 Sep	British Airways
25 Sep - 02 Oct	British Airways	direct
12 Sep - 14 Sep	KLM
20 Sep - 27 Sep	British Airways
18 Sep - 25 Sep	British Airways	direct
13 Sep - 14 Sep	ITA Airways
14 Sep - 18 Sep	KLM
05 Sep - 07 Sep	Lufthansa

Also check the deals for one-way flights from London to San Sebastian 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 San Sebastian in September from 321€

Return flights