2002 Peugeot Boxer Battery being drained

Ok, I'm having problems with a Peugeot Boxer the battery keeps dying.
So this van has a few problems when I bought if the electrics seam to be a rats nest of s--t I've after buying a new battery and it worked for a while then a few days later completely dead.
When I went to jump start it it took quite a few try's before it started it would start again when it was running for a while but if I left It half an hour it would be completely dead.
I also charged the battery for a couple of days and when I go to start it it ticks over but won't start needs a jump to start. So I thought the alternator was bad so I tested it by disconnecting the negitive when it was running and it didn't knock off so I thought the alternator might be ok. So I have come to the conclusion the is a drain on the battery that's why it won't start on a charged battery. So if any one can help you would be doing me a massive favour any ideas or a way to find what's draining the battery. I checked to make sure no light where on inside and out. And just wondering what resistance across the battery in omhs should read when the van key is out. Please help need to sort out the van has the neighbors are going mad it's been parked up for so long