The 'Pirates of the Caribbean' star has remained close friends with Penelope since they ended their six-month relationship at the beginning of 2007.
Penelope, who is soon to launch a fashion collection for Mango with her sister Monica, is said to have been keen on buying a home in London for some time after falling in love with the city.
The Spanish beauty previously dated Tom Cruise, with whom she also remains friends, as well as the gorgeous actor Matthew McConaughey.
Penelope is understood to be looking for a house that is big enough to accommodate all of her family when they come and visit, and Orlando jumped at the chance to help her find one.
A source told American Star magazine: "When Penelope asked him to help her find a place, Orlando didn't hesitate.
"He knew it would be a great opportunity to spend quality time with Penelope."
