Polly Pippin and The Invisible Secret

This is the third book of six of Polly Pippin and her cousin Alison set in London. They become friends and fall at little bit in love with Piers Knightly and his cousin Miles Winsor. After they meet the Freeflyers Event and Salute from the First Universe, strange and unbelievable things happen to them. They find themselves in the middle of the battle for the earth, against the Rebel Warriors from the Dark Universe. Two Freeflyers Event and Salute meet the girls and life is never the same. At times they find themselves back in time and it’s very scary.
Polly Pippin and Alison Rose live in a 600-year-old house in Byzantine Crescent, Docklands London, which is owned by the First Universe. The Rebels desperately want to capture the girls and the house, as it leads them directly to the invisible secret and the First Universe.
Lily and Lucy who are friends run the Brown Sugar Café, which becomes the meeting place. It is where they meet Piers and Miles, but everyone good and evil goes there.
They still don’t but Piers and Miles are twins of Zack and Knox who were stolen at birth by the Dark Universe. They were trained at Rebel Warriors, and are leading the battle to capture the earth. They often zap the boys to perilous places and pretend they are the UFO’s (Unidentified Flying Objects and eventually Fledgling Freeflyers)
Piers and Miles trying to rescue the girls end up in the crow’s nest of Blackbeard’s ship. Blackbeard attacked the Dutch ship and took the girls and the Freeflyers back to “The Revenge”. He thought Piers and Miles were Zack and Knox, and the boys went along with it. Davy Jones was invited to the party, but Event set him alight. Davy dived over the side, screaming, and threw out his stinking capturing net as he did. It landed on Miles and took him to his death in Davy’s locker.
The mythicals are Pendragon and Kylin, they are double winged dragonfly’s belonging to the fathers of the twins, Freeflyers Sreip and Selim. They can change size, and Pendragon can spit fire.
The two Lie detectors are known as Liddles, are strange creatures: they have no fur and their skin shines and glistens. Their eyes are huge, brilliant green and extraordinarily beautiful, with eyelashes to die for. If anyone tells a lie or a fib, they change colour, the biggest the porky pie, the brighter the colours.
Harry the hand, is devoted to Zack and Knox, and that's all it was, a large hand. On the end of each finger was an eye that stared fixedly, and a mouth of sorts, with thick luscious lips lay smack in the middle of the palm. The little hand stood on a dozen or so thin little pink legs. On his feet were knee length white sock and brown brogues, and he loved to dance the Highland fling. He was proudly dressed in a kilt, and in the sporran was a proboscis that flew out and prodded any one that upset him a little too hard.
After many more adventures the girls eventually got back to Byzantine Crescent they heard a splash coming from the picture of the castle in the hall. Event and Salute were standing in a puddle of water they had come from the moat. Rebels were following but Event killed the probe, and with the girls, was sucked back in courtyard of Camelot Castle.
The Freeflyers are trying to protect the earth. If the Rebels win, they will capture the Earthbeings to be warriors or slaves, and have access to the First Universe, which will make them evil controllers of the Multiverse.