Flat battery

Are you sure its dead and you don't have a bad earth or even a lazy starter motor

Get your battery load tested , may be a weak cell .

Does sound like a battery issue which may show up on colder temp. Days ,advise check for leakage to earth ,but probably going to be a battery.

Also make sure the boot light is going off every time the boot`s shut. If the switch is sticking, it will drain the battery.

Its not the battery because I only use the at the weekend. At stands all week untouched and it still fire up at the weekend. Its not the boot light, that doesn't work nbever has.it goes for weeks as normal with fully charged battery and then sauddenly one day it is flat

When you say flat is the engine turning over at all or do you hear just a click

If car is lying for that length of time and not used , it will eventually run down the battery , especially if it's an older battery . When the car is used at the weekend is it given a good run ?

The battery is totally flat this time not even a click. Two days before that I drove a round 20 miles.

Replace your battery

I'm gonna take it for a diagnostic

Well that,s quite pointless if you have a power issue it,s probably wiped any code.Have you checked your earth lead is good ? Probably better getting your battery checked out and a volt drop test carried out in case some thing is intermittantly sticking causing drain.

I'll do that first. Thanks buster