Where did Debussy compose La Mer?

Debussy began 'La Mer' in Burgundy in 1903 and completed it on 5th March 1905, which is the publishing date.

Debussy holidayed that year at The Grand Hotel (room 200) in Eastbourne, Sussex at which he arrived at on 23rd July 1905. Whilst there he corrected the proofs of 'La Mer' and wrote a replacement 1st movt. for Images book 1 which he called 'Reflets dans l'eau'. It's likely he also bought his favourite piano, a Blüthner, whilst in Eastbourne.