Steering is heavy and doesn't self-center, tyre pressures are fine so I'm thinking bearings.... How many places do people know of that just do the bearings and don't replace the whole hub? I know Aarons Autos & Mark Black do but they're 75 & 95 miles away. Are there any that people know of closer to Northamptonshire?
There was a company on ebay that were doing exchange refurbed ones i think, they included an extra cover for the bearing which should protect it a little more from seizing IIRC