Although Philip II, King of Spain married Mary I (d. 1558) of England in 1554, it would appear that the combination of these arms has no particular significance. See David Gaimster, German Stoneware 1200-1900 (London 1997), pp. 181-182 where there are Schnelles with different combinations of the Royal arms of England and the Royal arms of Spain. The example from the British Museum with the Royal arms of England (1854,8-16,1) illustrated on p. 182 is not moulded with St. George and the dragon.
(Manuscript label, on the inside of the cover, inscribed in sepia 44 spitzer)