Oh do I have a series for you!
There's like 15 of them and they're by Lauren Willig.
The first one is called, The Secret History of the Pink Carnation
The first book is about a young woman in present day London who is trying to figure out who the infamous spy The Pink Carnation is. Through reading old letters, she learns that the Carnation was a female spy who was at odds with a male spy named The Purple Gentian who always felt the need to swoop in and protect her.
It's a historical romance and I absolutely love this series!
Not a show (soon, I hope!), but there is the Pink Carnation series by Lauren Willig.. Similar concept as the Bridgestone books, but with a spy/mystery thrown in - and dueling modern/Regency love/timelines.
Lauren Willig’s Pink Carnation series is similar. Each book features a new heroine, but there’s an added mystery component.
Lynn Messina’s Beatrice Hyde-Clare Cozy Mystery series is also good.
It’s technically Georgian and not Regency, but the Lady Anne Addison mysteries by Victoria Hamilton are also romances.