I have an 53 plate STI and the battery on it is terrible, leave it for long than a week without starting the car and it will be flat, if i just have the ignition on for longer than 5 - 10 mins then it will be flat.

Can anyone recommend a decent battery that will last?

 

Halfords Calcium Battery HCB005 for £82.99. I put one in a couple of weeks ago as I had similar battery issues to you.

 

I opted for the Braille lightweight one. Keeps the charge better and saved a few kilos too.

 

HCB005 fixed all my starting probs.