So MoT has picked this up on the front as an advisory.

 

from what I gather it means that the front brakes are slightly different to each other (not very technical I’m afraid!)

 

i had new discs and pads pads less than a year ago.

 

firstly is the fix to the problem another new set of discs and pads, or go back to the original garage?

Fluctuating suggests slight disc warpage, fit new discs and pads to correct, disc quality is a factor in longevity so make sure you fit decent discs, I swear by Brembo but Pagid is good as well.