The "lions" travel to London to detonate their devices at the London Marathon. However, the streets clearly show signs for Sheffield traders - including many 0114 (Sheffield) telephone numbers. Additionally, the double decker buses are the wrong color.
When Barry is driving the group to the airport in his Citroen Xantia, he pulls over in a huff and swallows the key to stop them going. However, the key he produces and swallows is a Ford key, not a Citroen key.
Additionally, the car is fitted as standard with a keypad immobiliser, requiring a security number to start - so Omar's attempt to hotwire the car would not have succeeded in real life.