Short answer: No, the Atlantic Ocean is not "near" London in any practical sense—though it's the ultimate source of the waters that are nearby.
The Atlantic lies west of the British Isles, separated from London by the entire width of Ireland/UK landmass plus the Irish Sea. Water reaches London via:
So while London is a major tidal river port with maritime heritage, calling the Atlantic "near" is like saying New York is near the Pacific because the Hudson eventually connects to it via canals and the Great Lakes. Technically true hydrologically; geographically misleading.