The guards in the refinery are seen using American-made Thompson sub-machine guns but during that period in Britain they were far more likely to have used British-made Sten Guns or Stirling-Patchett sub-machine guns.
Brand plots the location of the objects falling 90/100 miles to the north but, for the apparent scale of the map he is using, his compass setting is much too small and would produce a radius of perhaps 10 miles at the most.
At Winnerden Flats, when Quatermass is being escorted to his car, a guard, who has turned the car around, can be seen in the driver's seat. In the following shot, when you would expect the driver to get out and make way for Quatermass, another guard comes from the right and opens the driver's door to an empty car.
When hurrying to the phone in the Pressure Control Block, McLeod puts down his jacket, which slips to the floor. It appears to have returned to where he originally placed it when he retrieves it in another shot, however.
Quatermass and Marsh are seen supposedly driving north on the Carlisle road and just about to turn left. Yet earlier in the film Quatermass is shown on the same road, also driving north (from London) but in the opposite direction.
After the opening paragraph of the newspaper report detailing Vincent Broadhead's purported emergency Middle East trade mission, the remainder of the piece details postal voting in badly-formed columns; similarly the accompanying texts about King Leopold and Big Ben bear no relation to their headlines.
The goof items below may give away important plot points.
The internal continuity lapses towards the end. Quatermass encounters the motoring couple when returning from his Ministry funding meeting on the first evening (March 14). He and Marsh investigate Winnerden Flats the following day (March 15), whilst the next (March 16) sees the House of Commons visit and tour of the synthetic food plant in the afternoon (where Marsh is correctly said to have been hospitalised "yesterday"). Quatermass meets Hall a few hours later, who insists on questioning the Winnerden Flats locals before filing his story for the morning edition of his paper. On their arrival Quatermass is recognised from "two days ago" as the residents enjoy their St Patrick's Night celebration, which implies a sudden day's leap to the last few hours of March 17 (a poster gives the party's time as 8-12pm).
In the shot revealing that the Police Commissioner has 'the mark', he is consulting a typewritten checklist. Closer examination reveals this text to be the repeated phrase "Now is the time for all good men to come to the aid of the party".