Hello my keyhole still has a mirror modifier on it have i missed something and if mark the seam will that make a problem with the UV mapping?
You didn't miss anything - Rather I seem to have applied the mirror modifier while not recording (?) 🤔
Conceptually I like to apply a mirror modifier for a central object because the mirroring is obvious and unappealing. So I will use the mirror function to generate the majority of my shape (as seen in this lesson) getting two halves for the price of one. Then for the last stage I will apply the mirror modifier and make slight adjustments to each side, resulting in a non-mirrored final piece.
The same principle applies to the mirror modifier and UVs / textures. Functionally the mirror modifier works like modeling: The UVs and texture will simply e mirrored to the other side of the object. As mentioned earlier this kind of duplication is obvious and usually a negative characteristic accept for particularly resource-stingy situations (like n64-era models and mobile games). Therefore I also like to apply mirror mods on central pieces for texture uniqueness.
I'm not sure why I didn't record this action...Must have slipped through production cracks. Sorry for the confusion!