Sounds like bearing failure.
Check by seeing if there is any vertical movement between the moving stainless drum and the fixed outer drum. There should be no vertical movement between them - if there is the bearings have failed and will soon collapse. Changing bearings is an involved job, only attempt if you are mechanically competent.
As for changing the bearings.........
Power off, remove covers. Disconnect drive belt, remove drive pulley. Remove heater, thermostat and pressure switch. Check if drum splits at front, rear or the middle. If the drum is a plastic welded one- ie one which doesn't split, then its game over. If it splits at front or middle, drum will prob. need removal from machine. This involves dismantling the suspension and damping system and removal of door seal and concrete weights. Undo the drum fixing system - either a clamping ring or a series of peripheral bolts and split the drum.If the drum splits at the rear, removal from machine probably not required. Remove the clamping system and pull off the rear plate. Seal and bearings will come away with the plate. Seal needs to be dug out with a suitable lever and the old bearings hammered out with a punch from opposing sides of the backplate. Refitting is, as they say, a reversal of the above process.
Thats it in its briefest form. You do need to have significant spanner skills. If youre the type of guy (or gal) who works on their car, it would be no problem. If you're a novice, dont even go there, get a professional to do it, but its going to have to be a judgement call taking into account the high labour costs (at least £120) and the condition and value of the machine.
Repair and service your own washing machine. Go to www.2ndwave.co.uk/manual.html
dannyboy, November 2008