Are they online? If they are then check their website for contact details. look for an address and land line phone number. Phone them and ask questions like what is the equielant of henleys size 5 for UK sizes? Or what company will he be using for delierly and how much it will cost (or ask how much it costs him of his delivery is free) and then check with the company and ask them how much approx it would cost to send your order. Also check the the area code for land line against the addres to see if the area code matches the town. Also use one of the domain name registration sites to check who their website is registered to and what address.
Also if they have told you how many they have in stock then get them to put x amount to one side for you and then an hour later email them off a differant email account and say you are interested on buying some how many do they have in stock to see if they take off what you ordered or if they say a differant number completley then it smells a bit fishy
not too sure on your last 1 but the first bit of advice is excellent for newbies.
they may not have taken it off for alot of reason: you spoke to 1 person and they have 10 staff, who hasnt told anybody about this deal, since you have not yet paid, it has not been taken off their system a whole lot of other reasons come to mind