I love Zara and Imogen from your list.
On similar levels of 'uncommon-ish but reasonably well known names':
Asha, Anika, Alanna, Adele, Amy, Anya
Bronte, Belinda, Bryony, Bethan
Clarissa, Calista, Cassia, Cerys, Carys, Cleo, Cherry, Claire
Daniella, Diana, Damaris
Elora, Evadne, Erica, Effie, Esther
Fenella, Fern, Fleur, Faye, Faith, Fiona
Giselle, Gemma, Gretel, Giovanna
Hester, Honor, Hebe
Iona, Ingrid, Inez
Jacinta, Juniper, Joelle, Juno, Jessamy
Kiki, Kate, Kendra, Kerry, Kirsten, Kiran, Karensa
Liara, Lorna, Leonie, Larissa, Lara, Lux
Marta, Mirren, Meredith, Miranda, Marianne, Melinda
Nicole, Naomi, Noelle, Nova, Nadia, Nadine, Natasha, Natalie, Noa
Opal, Octavia, Ondine
Pippi, Pandora, Paloma, Payton, Paige
Quinn
Rowena, Rowan, Robyn, Remy, Romy, Romilly, Rhiannon, Ria
Saffron, Sorrel, Sadie, Saskia, Susannah, Stella, Samantha, Stephanie
Tamara, Tanya, Thea, Tamsin, Taryn, Tegan, Tara, Tessa
Una, Ursula
Verity, Vanessa, Vivianne
Winona, Willa, Wanda
Xanthe, Xenia
Yvette, Yvonne, Yolanda
Zia, Zeryn, Zillah, Zelda