There's masses of space up front but, despite the Mustang's sizeable proportions, the two rear seats are cramped. Children and particularly short grown-ups will fit, but more standard-sized adults won't unless they contort their bodies unnaturally. However, there is a bit more head room than you’ll get in the Audi TT, while the long doors mean access is a little better than in the TT or BMW 2 Series. Even so, an Audi A5 is even more comfortable.
Still, it’s not all doom and gloom. The Mustang gets Isofix mounts in the rear, so two child seats will be secure there. Good luck explaining it’s a sensible family car to your better half, though.
Officially, the Mustang has a bigger boot than you get in its immediate rivals; there’s 408 litres of space with the rear seats in place and you can fold those seats down when you need to carry longer items. However, the narrow opening and high load lip mean it’ll be difficult to load bulky items. Despite its smaller and shallower load bay, in this respect the TT, with its hatchback boot, is actually more practical.