Honestly mate. Don't bother, coilovers make the car exceedingly harsh and you really don't want to be going lower than about 35-40mm as it makes the car drive like crap, puts the camber out of tolerance and will destroy the lower arms at an alarming rate.

My brother is planning to ditch his coilovers and return to a strut and spring set up while the car is off the road.

Appreciate that's probably not what you want to hear though