This Series 3 I have just seen on ebay may or may not be stolen, but it is definitely a ringer. https://www.ebay.co.uk/itm/326498435624?itmmeta=01JVSVR5P7EFNQ7SBQ866PHDAT&hash=item4c04d2c228:g:LqMAAOSw19Bn32uR There is no way this is a genuine...
Alternator won't really help much here. Is your battery, big, beefy and healthy?
How long are your jump leads? They need to be beefy too, at least as thick as your middle finger, or there about