Our 1989 90 has a knock/rattle that can be felt through the steering wheel when at speed and travelling in a straight line. It passed it's MOT in January, so would assume (!) that nothing major was wrong. Apart from checking the obvious joints, what else could this be? Where should I be looking. Hope it's not the steering box...

Assume nothing, either get it to a garage to get it checked out. Or get it up on axle stands and start going through it bit by bit.

Cheers

As above ,also check front UJ's one could be on the way out.