diagnostic problem

my defender has developed what I can only describe as lumpy steering feels fine then almost as if its starting to seize up then fine again all within 200yds , i've had it to the local garage who say its either the PAS pump or the steering box but not sure which
Anyone had a similar problem as its an expensive gamble to see which one it is

Worth checking the two small UJs on the steering shaft

Same as above. That's what happened to me. I now spray them liberally with WD40 on a regular basis as they get covered in salt water a lot.