If you require a JOIN, why does it need to be halfway? Get the maximum length available plus whatever is left.

If you can have the join align with another vertical line. E.g if you have overhead cabinets or window edge. I would avoid it being in middle of stove as that is the dirtiest part.

What about two joins? Have the maximum length centred and equal sized smaller pieces on each end.

We don’t have any overhead cabinets but do have a range hood. I felt 3 pieces, the middle section over the cooker and a section either side. My husband thought 2 pieces joining in the middle.

This is a photo of the kitchen and why my husband says 2 pieces. Sorry to be a pain about it.

If it’s all one ht I can see why middle would be best
3 would allow the stove section to go up to the range hood.

After seeing your kitchen, I would go with three pieces. Two the length of the bench, and one the length of the cooktop, extending to the ceiling behind the splash back.
The kitchen looks too bare for just one straight piece.
You could maybe install open shelves either side of range hood, or overhead cupboards.
I have attached a picture of a kitchen with glass splashback. You can just see the lines in the glass either side of cooktop.

*should read, extend to ceiling behind the range hood.

Other photos

Thanks, the splashback extends the same height as the rangehood right across. I do like your idea of to the ceiling behind the hood. Thanks

Will the splashback be too high if its range hood height all the way across the wall? I think it could be. Sorry, just my thoughts.