Bloomin Ebay Urgent Advice needed!!!

[gaza121]

Chaps

Advice needed pronto!!!
Won a caravan on Ebay last night with a winning bid of £4500 (reserve met and have emails from ebay to say I have won item).

Recieved an email off the seller asking if I would be ok paying £5000 for the van as its a bargain!!!!

Where do I stand legally on this is she obliged to sell etc and how would you proceed

Thanks in advance

Gaz