Lea,

I had EXACTLY the same symptoms a couple of weeks ago when my battery gave up the ghost.

I had left the car for 3 weeks whilst we were on holiday and had the same problem. A quick call to my mechanic confirmed that I could jmp start the car provided no electrics were on, just the starter and I got her going. A short drive later and all appeared happy again. However, several days later the battery was flat again.

I thought I'd try another battery over the Mercedes OEM fitted, so a trip to Halfords (UK motor factors) and we were up and running again. This battery has a slightly higher cold crank rating to the OEM, so fingers crossed.

I've also invested in a solar powered trickle charger.

Greg