New internal door

Did you check the height aswell as you could have a metric door so the nearest size would be 826 x 2040 and this could be trimmed to suit your needs Alternatively you could have a new lining fitted to accept the size you require

If the door is veneered on the sides/edges then it may not have enough veneer if you remove that much from the sides to fit the existing frame. If it's not veneered on the sides then cutting to fit will be fine. Otherwise exchange the door for a more suitable size or change the lining which requires cutting one side of the wall back slightly to fit the new lining. You'll need new architrave too though.

The simple answer is yes , but because it’s a veneered door you will need extra sharp tools. I would if you have access to one is take 14mm off each side using a plunge saw that gives 28mm off , then mark door where it needs more off and either use an electric plane or if you have access to one a router. The router way , you can clamp timber to the door to stop you going deeper that you need . Another option is to remove the architrave and bang packers between the door lining and the wall or stud so you even the gap through the length of the door at least this way you will be removing an even amount off of each side of the door .

The answer given is sound However, I would simply buy a solid timber door. Engineered veneered doors have a half inch solid timber edge This could be compromised if you cut a fair bit off the door