I’m currently in the process of buying a 2019 1 litre ecoboost ford fiesta. The car has got full service history and has only done 17k miles which I don’t think is too bad. But I have heard these engines can come with all sort of problems so I’m looking for advice whether I should actually go ahead with buying the car. 

Hi Robbie, welcome.

There are loads of threads on here covering basically the same question if you have a look around. This one for example covered most points, suggest you have a read and come back with any further questions:

On "your" specific car. The wet cambelt will require changing at 10 years max irrespective of mileage (from £950 at an independent up to £1800 at Ford dealers). Many recommend changing early, at around 8 years.

The low mileage is not necessarily a good thing and suggests short journeys where the engine never gets properly warm. Under those conditions regular oil changes are recommended and I would look for evidence of (at least) annual changes.