What might account for a higher level of euroscepticism in great britain than in continental european nations?

One possibility is the geographical difference and the effect it has on people. Great Britain is an Island so it can feel relatively safe (see the fate of GB in WW2 as compared to the rest of Europe) and because of this it can afford a more separatist policy. continental Europe however need a closer cooperation between the neighbours, as they share physical land borders, and only peace and a close cooperation can give the feeling of safety (for example to German neighbors, close economic Union is the best defense against a possible attach from Germany).