quoted times in the books and table mean nothing, a job to a specific garage takes as long as it takes depending on individual mechanics knowledge and ability to improvise/use of tricks to cut corners etc
basically anything written down will be a 'book' time and as such costly.the actual time taken will never be quoted and the garage will simply charge by the 'book' or close to it if they are feeling 'generous'
example, clio mk 1 heater matrix, 6 hour book time, actual time taken 40 minutes including tea break