This cache is not at the listed coordinates.
This cache is great for husbands, perfect for when the wife is taking forever at the shops.
You will be inside with the comfort of air conditioning for most of the time and then you will wander outside to retrieve the final cache, which is a black magnetic nano on a piece of art.
To obtain the final coordinates, you will need to wander Garden City using the map provided (although less adventurous methods are available). Find the shop name that corresponds to the matching shop number. Using the given letter number, convert said letter to a number. For example, if the clue is 'Shop 1805 Letter 5' and the name was Willy Wonka’s Chocolate Factory, then required letter is Y, which is converted to 25. Follow any additional equation instructions following this.
I have tried to choose a mix of shops from different sectors such as jewellery, services, food, electronics and so on, just to keep it interesting. The map below is vital, if you forget to print it, it is available for free at the information desk or on information boards at most entrances of the complex. It has all the shop numbers on it. Good luck!
Revised puzzle, up to date as of 3 November 2022
Changes since the last revision.
SOUTH
(Shop 143 Letter 5) – 2
(Shop 310 Letter 9) x 4 – 18
(Shop K33 Letter 3) + (23 – 39) x (7 - 5) + 32 - 15
(Shop 96 Letter 2) – 5
(Shop 70 Letter 5)
(Shop 5A Letter 2) x 4
(Shop 75 Letter 5) + 21 – 6 + 2 – 14
EAST
(Shop 172 Letter 2) – 20
(Shop 320 Letter 6) – 18
(Shop 158 Letter 4) – 10
(Shop 123 Letter 3) - 1
(Shop 97 Letter 3) + 2
(Shop UC Letter 2) + 1 – 8
(Shop 183 Letter 5) – 10 + 68 – 66 + 4 – 7
(Shop 93/94 Letter 5) + 7
Please feel free to contact me if you need to. And don't forget to enjoy the puzzle! 
Congratulations to Chwiliwr and Gwiber on joint FTF!