Celia arrives back on UK screens next week as she turns up in Summer Bay to see her niece Roo (Georgie Parker) tie the knot with Harvey Ryan (Marcus Graham).
Fans can expect Celia to stick around in the Bay for a few weeks, giving her a chance to re-connect with her brother Alf (Ray Meagher).
Spence told Digital Spy: "I was thrilled to be asked back again. I've always loved playing Celia and that's not going to change. I was last on the show in 2005 and it was wonderful to come back. I was filming across a couple of months, so Celia will be around for a while."
Discussing Home and Away's recent achievement of reaching 25 years on the air, the actress continued: "It's fantastic - the show just keeps on going. It's a wonderful show and I'm pleased to be in it. It's an incredible milestone in this industry.
"If I knew the secret of its success, I'd be producing television shows for a living, but for Home and Away, it has to come down to the people and the stories. It's well acted and well shot, and the sea and surf in Summer Bay has to be one of the best-loved landscapes on television."
UK viewers will see that Celia takes a while to warm to Harvey when she reappears on screen next week.
Spence explained: "Celia arrives for the wedding of Roo and Harvey with Morag. Colleen also turns up, so it's a big reunion for Alf and his sisters. I can hint that Celia has a lot of opinions about Roo's choice in Harvey as her partner.
"Her very first meeting of Harvey is a funny scene. I don't want to give too much away, but I will say there is a case of mistaken identity and Harvey is in his underpants!
"Celia is absolutely supportive of Roo, but I don't believe she will ever think anyone is good enough for Roo. That means Harvey has his work cut out for him winning over Celia."
Spence noted that it was "wonderful" to be reunited with co-stars Ray Meagher, Cornelia Frances, Lyn Collingwood, Lynne McGranger and Emily Symons when filming her scenes.
On the new cast members she met, the 64-year-old continued: "I just adored working with Georgie. She has terrific energy on set and our scenes were always enjoyable.
"I'm impressed with all of the new cast members as I've watched the show and enjoyed their work. I did a bit of work with Dan Ewing, which I loved, and I found the entire younger cast to be so welcoming and wonderful."
The actress also told Digital Spy that she has many fond memories of working on Home and Away, having first appeared on the soap in 1988.
She said: "It is hard to pick any particular memories from all the wonderful years as Celia. She has passed judgement on all of Summer Bay's residents, which was often very fun to play. I have very fond memories of returning for Alfred's 60th birthday as it was a lovely reunion with some other cast as well."
Asked if she would be open to returning again in the future, Spence replied: "I've always loved playing Celia, so the answer is yes."
Home and Away airs weekdays at 1.15pm and 6pm on Channel 5 in the UK, and weekdays at 7pm on Network Seven in Australia.
New! Digital Spy Soap Scoop video - watch Amie Parker-Williams reveal the biggest storylines on the way in Coronation Street, EastEnders, Emmerdale and Hollyoaks next week.