My daughter has recently bought a 2011 1.25 Zetec Fiesta with around 75k miles

All is well with the car however I don't think there's any paperwork to support whether it's had a cambelt change

Wondered if there would be a date code visible if I removed the plastic cover at the top or some other way of telling.

Pretty sure the mileage is genuine so I'd imagine it must really be due for a change by now - even if I knew what make the factory belt was I'd have some idea

Any advice welcome

Any branding is likely to be worn off by now unfortunately.  They don't have date codes.

Recommended interval is 8 years or 100k miles on these.

In my opinion. If you are unsure about if the cambelt and water pump have been done, given the car has passed the time requirement but not on the mileage, IF it was my car I'd get them changed for peace of mind. If you get your preferred garage to do the job, at least you have an invoice to look back on for future refrance. 

Worth getting it done anyway as chances are with the long service interval it'll need doing once - and only once - in your ownership so you might as well do it now for the peace of mind given the uncertainty. Furthermore, it is quite a straightforward one to do so not too expensive (in contrast to the 1L Ecoboost at least).