Being picky, whilst I know that ATC can't tell you to land, they can tell you if you're going to, which runway to land on. I had no doubt that you would question the instruction / clearance, my point was that sometimes one must question, or even in extremis disregard an instruction and announce that you've done so. The sin, IMHO, would be to do your own thing without talking.
w.r.t. Eyes open, a couple of weeks ago I was rejoining at Old Sarum, half way between Alderbury VRP and the airfield, I heard a Warrior (faster than what I was flying) call same join behind me. I made a precuationary call reminding Warrior that I was there. They couldn't see me, and did a couple of orbits until they did (I was slow, but painted bright yellow with a 30ft span, same level). Assuming other pilots have their eyes open isn't always a safe option. (Fully accept my RT was totally non standard at the time, but infinitely preferable to a PA28 up my backside, so far as I know neither the other pilot nor OS Radio had a problem either).
G