The subject exhibits further doofus behaviour:

So as my first eBay auction draws to a close, giving me a potential net profit of £5.50, I have learnt an important lesson. When the buyer has attempted to give you the money don't get all confused in PayPal and accidentally press the button that means you refuse to accept payment. Doh! Hopefully they'll resend it when they see my apologetic email apologising for me being such a doofus.