Hi.
Yes it should have been. A small adapter is usually fitted either on top of the gearbox, under the the air box. Or in some cases behind the light cluster. Result is that the speedo is converted to mph and the speed limiter is usually removed.
The odometer then calculates in miles and the speedo is about right with a variance of about two miles per hour either side. Normally an mph sticker is then put over the kph, or an m over the k.
You can check what's going against a satnav. Maybe you are just minus a sticker over the kph. If the car came through Ireland initially then it will be in kph.
Regards.