It's UK to Uk though so it should have arrived, even if sent by Pony Express. If someone got shirty with me when I asked for tracking number or proof of postage I wouldn't wait any longer, I'd simply file a claim and let ebay/paypal sort it.
It's been in the UK postal system for two weeks, they aren't that slow, the guy said he'd posted it the next day so I think I'd be asking questions. If you ordered from Amazon or other online outlet you'd be asking questions.