Refurbished iPhones etc

Q - "Is Groupon the best site for refurbished stuff?"
A - No it isn't.

Q - What I need is decent state for a low price, with a proper business invoice.
A - Try "Certified Refurbished" products on Amazon.

Make sure you register your VAT number with Amazon before you buy, that way you'll get a proper invoice.

You could check to see what Cashconverters has on hand in one of their 30 stores in Belgium (7 in Brussels).
More info:
http://www.cashconverters.be/fr/who

Not used it, but I do know of this site-
http://www.irepairshop.be/

Perhaps someone on here could give feedback.....?

You could try Amazon maybe or eBay but the issue is that you're relying on the vendor being honest about these items we bought a second hand iPod in the uk to replace a damage one but even though its new the battery is rubbish clearly incorrectly charged up a few times and now depletes fast.

You could also check out Carrefour they sometimes sell the items off when stock changes. I don't know if Apple sell refurbished items check their website I doubt it though

Apple DO sell refurbished items and when they have any available they appear on their website - they usually sell very quickly though.