The singer tied the knot to his dancer fiancée Chloe Tangney on the Isle of Bute on Saturday.
Simon Cowell, Sir Elton John and Olly Murs were among the celebrities reported to be in attendance at the ceremony held at the Mount Stuart estate.
The chapel on the grounds of the 19th century mansion is where fashion guru Stella McCartney wed publisher Alasdhair Willis in 2003.
The luxurious 300-acre venue, which is the stately home of the seventh Marquess of Bute, was completely closed to the public over the weekend and reopened today.
Guests were reported to have been seen boarding a double decker bus displaying "Mount Stuart" on the front, which whisked them off to the star-studded ceremony. Celebrities and islanders took to social media site Twitter to congratulate the couple.
Rochelle Humes, of girl band The Saturdays, tweeted: "What a beautiful day yesterday was. Such a blessing to see people so close to us getting married."
JB's former band mate Oritsé Williams wrote: "Well done JB Gill & Chloe Tangney.
"You both looked beautifully happy last night! I can still hear the sound of bagpipes in my ears."
Rothesay resident Eddie Telfer said: "Congratulations and I hope you all enjoyed your time on our lovely island and Mount Stuart house."