South Western Hotel Southampton

The hotel overlooking the White Star dock in Southampton, used by many first class passengers, including Ismay and Thomas Andrews the night before Titanic sailed

Genuine, vintage real photo postcard, mailed in Southampton in 1911, now on eBay

I hope the seller can show that it was a 1911 stamped postcard.

The South Western Building is still standing, though it is no longer a hotel.
The South Western, in 1912, was where many of the passengers came to stay before they embarked on Titanic; it was the equivalent of Southampton's semi-pricey DeVere Grand Harbour Hotel.
The card carries a clear postmark of 3.30 pm, 4th May 1911, tied between 1d stamp and the card, and was mailed to an address in Sydney, Australia.

As for the South Western Hotel, I believe it has quite recently been converted to flats, still bearing the South Western name.