Note that cars in the UK are generally more expensive.
Rule of thumb is that for most cars, take the US $ price and just change the $ to £. However, BMWs seem to be less expensive that that in the UK -- perhaps because BMWs have been marketed to a higher level of luxury prestige in the US.
Of course, that base model Fiesta in the UK comes with a 1.25L engine with 60hp and only 7% better fuel economy than the 1.6L engine with 120hp that is similar to the US Fiesta engine. Rear center head restraint, spare wheel, and curtain airbags are options. And if you want an automatic transmission, it is a £1,000 upcharge for an inferior 4-speed torque converter unit, available only with the 1.4L engine with 96hp.
On the upside, UK Fiesta buyers can choose one of three amazingly fuel efficient diesel engines, and also have options like parking sensors and rear view camera.
As far as defects go, the US Fiesta is at the very beginning of production, with a completely new supply chain. It is well known that first year of a new design cars tend to have more defects than later years of the same design (though a first year Honda is still likely to be more reliable than a later year Jaguar). Presumably, if you bought one of the first of its kind, you accept that small additional risk.
Remember also that European car buyers may be more tolerant of reliability and servicing issues; after all, they buy a lot of Volkswagen and Mercedes-Benz cars that do not have a great reliability reputation. Plus also French and Italian cars (check out the YouTube video on changing the headlamp bulb on a Renault Megane).