The cloud might be a mythical place where your data floats round in the ether all day, but from a practical perspective that data must be physically stored somewhere, and you should find out where that place is. While it might not actually matter to you so long as its in safe hands somewhere, there are data privacy implications which are more important in some sectors than others. For example, if your data is stored on servers located within the US that data might be able to be scrutinised by government agencies whereas the same would not happen within the EU. Even worse, some servers may be located in other countries with poor security provisioning, and your (and our) obligations under the Data Protection Act 1998 state that data should not be transferred outside of the European Economic Area unless proper data protection is in place.
Apart from the geographical location, you’ll also want to make sure that the data centre where your data is being stored is adequately secured against physical threats also, e.g. fire, theft or other loss. For the record the Affinity servers are located within the Hetzner facility in Falkenstein, Germany. It's an ISO27001 certified facility and you can find details about the data centre here.