I think i know the answer, google search returned nothing, if I start a reduced daily rest on Saturday & my 9hrs isn’t complete untill 00.10 on sunday, does that reduced rest count for the previous week or the ‘new’ week. Thanks 
If I understand correctly, then you are asking which week the reduced daily rest falls into?
You are allowed up to 3 reduced daily rests in a working week. In this case a working week is the time between two weekly rest periods. It is not the fixed week 00hrs00 Mon to 24hrs00 Sunday.
Ah, yes, i really need to get grips with which rules fall into the working week & the fixed week. Anyway, that covers me for now thanks 
Apart from weekly rests, the fixed week is important with the 10 hr driving day. You can have 2 ten HR drives in a fixed week.
So having a weekly rest does not reset your ten HR drives. A weekly rest does reset your reduced daily rest.
Just to add that a fixed week starts at 00:00 monday, the way your question read made me think you expected it to be 00:00 sunday though I may be assuming that.