2007 C70 Wont Start

[DLM48]

Went out to my C70 today pressed the remote and totally got no response

Slipped out key blade and opened car

Put key blade back in and put the whole thing in the ignition slot

NUFFFFIN

Key would not now come out of course

Opened bonnet and got out my battery charger

Connected it and it said 0V for the battery

As my V70 is now off the road for the winter its battery was available

Used the jump leads and the C70 came alive PHEW!!!

I was driving the car the other day and it was running fine the only thing I did that may have discharged the battery was unlike what I do normally I left my USB charger in the Cig Light Socket but I thought that was OK as it was not active unless the ignition was on

Also when I first connected the V70 battery to the C70 the radio came on

Also when I open the door the bottom text part of the instrument panel (miles etc) comes alive for a minute or so I have not timed this. It does the same when I slide in the key but for much less time

Charged both batteries connected together until the C70 one was about 10V

Then swapped batteries putting the recently charged V70 one in the C70

Reconnected battery charger

Everything works apart from the starter motor

When I try to start the C70 I get a MMMMMM noise but no activation of the starter motor


HELLLLLLP PLEASE