there is an earth starp that goes from the battery to the front shut panel near the n/s head lamp. this terminal must be clean and make very good contact, they often burn out or corrode away and are ignored.this prevents teh battery fully charging and causes starting issues
have you checked the boot light ?
Is the radio genuine or aftermarket ? is it wired correctly
Under the bonnet there are two yellow relays for the engine manegment system, try removing them when you park the night before and refitting them just before starting in the morning, if the battery is fine then one of the relays is faulty partially draining the battery overnight.
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