"I've finally made it on to the ground. It's quite a daunting journey from the UK and so nice to be here - I'm taking it all in."
It will be a short visit, though, as she flies out on Sunday.
"My mummy duties await me," she said, adding that daughter Scarlett's fifth birthday was only a week away.
Melanie C celebrated her own 40th birthday with a large group of friends at a concert at the Shepherd's Bush Empire in London.
"A lot of friends came up on the stage to join me - and of course we all partied until dawn."
Tomorrow, she will perform six songs as well as teaming up with Keating for a duet. "I'm excited about getting out there to perform with the orchestra," she said.