disco starting problems

My Disco has been off the road for the last 3 months due to replaicing alot of bits. I also fitted a larger capacity battery, when I tried to start it the bloody thing would not go can anyone HELP????? the weather is going to turn bad in Ireland soon and i cant stand driving the mercedes i also have. other key problems are that the central locking does not work when using key fob, as soon as i plug in alarm cable the siren just goes off (annoying the neighbours) Are my problems down to the spider under the radio that is causing my problems, thanks for any advice in advance.