Well unless I'm very much mistaken to use a 32bit browser, like firefox, and other 32bit java applications you have to have 32bit JRE installed. I've removed it to test however and it makes no difference to the launcher. Same error, same error log.
I've also searched for MD5 mismatches on the forums, and various other keywords like checksum, and have found people being told to disable their AV and firewall which I have already done.
Thanks for the suggestions Hashful but could you point me to any threads that have solutions other than those?