If you have any play in the hub it's too much. You need to adjust a cone to remove that play. While your there you should go ahead and service the hubs. It's been a few years since Raleigh used sealed hubs and the grease is very old now if it's never been done. If you have never serviced a hub or really know what you're doing you should have this performed by the mechanic at your LBS. Done incorrectly can lead to hub damage and personal injury if the wheel should lock up on the axel.
As for the sealed hubs, no there not cassette bearings but if you look at the cones you will see rings that contact and spin with the metal bearing shield. This does provide a seal from water and dirt and is quite effective.