What are the best springs for going slightly lower than standard

My R is standard ride height on standard springs but super stiff becuase of the many parts fitted
Gab super rally shocks
Poly bushed
4 point under brace
cusco strut brace
Welded front arms
Whiteline anti dive kit
Whiteline antiroll bar

Want to lower it slightly but only slightly .  we are talking 10 - 15mm at the most

What would people recomened ?
What are the whiteline springs like?

Whiteline are good but lower around 30mm range.
If you only want loose 15mm you probably going need get custom springs made as I never seen pre-made kits with 15mm drop.
Springcoil.co.uk can do custom springs by using current springs as guide & creating new spring with specific height adjustment & spring rate adjustment that might be required.
Have used them before & they do quality work but you looking at around £50 a spring for custom jobs.