The train station platform signs for the hospital and the main line are missing when Steed first runs onto it as he's trying to rescue Mrs. Peel, then return in place for the next time the platform is seen.
Mrs Peel changes place with Miss Thirlwell in the "operating theatre". Mrs Peel is a brunette while Miss Thirlwell is blonde but nobody seems to notice the sudden change of hair colour.
The display on the wall showing the radar outage area is the same as the clock on the operating room wall minus the hands, but the spindle is still seen in the middle.