Yes the phones are sim free, if you look on the site it explains this somewhere
I'm waiting for a new phone and as soon as Nokia have it on their site I will buy it from them, buying direct from nokia means you can be sure you have a UK version handset, websites like mobilebee.co.uk have there handsets shipped from Asia to USA then to UK, this means the Asian warrenty is worth jack in the UK as Nokia no longer has an international warrenty, if you needed to have the handset fixed you would need to send it to the USA who then in turn send it back to ASIA to be fixed

Secondly you may also get stung for tax when it comes through UK customs, making the handset about the same price as buying it sim free from Nokia or Carphone Warehouse
I'm not saying all online sellers are importing there handsets from ASIA, but I wouldn't run the risk. I have an N91-1 and in India the N91 is a N91-5, N91-5 has no wi-fi or 3G, I'd hate to buy a handset online and find it has come from a coutry with no wi fi or 3g or lacking something else