Help me find an old book

[ChinookPilotsGoVertical]

As a kid in the early to mid 80s I had a book I really enjoyed & would love to read again.
Obviously I can't remember the title or author, though I think it was a female author.
The plot was that a family moved from a city to a house in (I think) Devon - there was a mum & 4 kids & I think their name was Macie.
Eventually they discover a passage from the house down through the cliff to the beach & uncover a gang smuggling some kind of synthetic sweetener. Naturally they help confound the smugglers.
I appreciate that it's not much to go on but it's over 35 years ago, if anyone can help I'd be very grateful.

Grr, typo, the name was Mackie, not Macie. Also I think the paperback had a mostly green cover with a black & white drawing on the front.

The Young Detectives by RJ McGregor?

That sounds oddly familiar but I think I’m just conflating it with the many Enid Blytons I read as a child. And it’s not one of hers.

Sounds like one of the "adventure of..." books by Enid blyton

I remember a book like this too with the finding the passage down to the smugglers cove but the artificial sweetener isn’t ringing a bell.

Any of these:

https://en.m.wikipedia.org/wiki/TheAdventureSeries

Theclockticksslowly is right - the Mackie family is The Young Detectives! It didn’t click fully with my memory when I looked it up on Amazon though, tempted to order a copy to see if it’s the one I had!

The mystery of the smugglers cove

@theclockticksslowly, I think you're the winner! Thanks very much! I agree with the posters who suggested Blyton's "Adventure" series, I devoured those as a kid & it is similar but Theclockticksslowly has got it I think.
Thanks to everyone who took the time to reply.

Yay, I love these types of threads!

Even better, my wife found a copy on eBay & ordered it for me!