I certainly believe there is some truth in this certainly for the London midways. In particular these are highly dependent on foreign tourism and this has dropped since the attacks last year. If you look at the advice the US government is giving out on travel to the U.K. for example you can see why tourist numbers may be dropping:
“Exercise increased caution in the United Kingdom due to terrorism.
Terrorist groups continue plotting possible attacks in the United Kingdom. Terrorists may attack with little or no warning, targeting tourist locations, transportation hubs, markets/shopping malls, local government facilities, hotels, clubs, restaurants, places of worship, parks, major sporting and cultural events, educational institutions, airports, and other public areas.”
Regarding midways in other locations they are not all dependent on foreign tourism (Birmingham, Manchester etc) they are aimed at the domestic market and I believe this as well as developing areas such as India are where the new midways are going.
The investors seemed to accept this explanation from Merlin, it’s when they attempted to explain a drop in Resort theme parks visitors on terrorism that they lost confidence.