I vote for a full width mirror.
But I would get a local glazier to do it as then they would be responsible for getting the sizing right and fitting.

@byronec84 Thanks for sharing, this looks great. Did you get it from a glazier? Wasn't able to find many this size off the shelf.

@jonathan Thanks Jonathan. Very good shout.

I'd go to a glazer and get them to install a mirror. will make the room look a lot bigger

I would put a mirror in there from about waist height up to above your head (how much do you want to see while showering?), with tiles around it as a border to limit the amount of cleaning you will need to do. Definitely have your local glass company do the template and installation. The walls will probably not be straight and therefore the mirror should be measured and fit accordingly. Installing a heat pad behind it will keep it from fogging up but your electrician may not be willing to do this, and it will need a great deal of waterproofing as well.

This is a great project with a wall to wall mirror above the bath. Get also some interesting pendant lights to reflect the light and make a design statement. As for the steam problem, you can always install the demister pads, they work great and they’re quite inexpensive. You can find them here https://www.victorianplumbing.co.uk/warmup-mirror-demister

I did this in my bathroom, it was quite pricey but worth it to get a seamless finish. Me and my tiler profiled it ourselves and fitted it but would rather not do that again!

In would definitely go for a full mirror, will look very effective! And like some have said will defo make the room look bigger.

I measured and ordered the mirror glass from my local glazier, it was under 60 pound. My partner stuck it on the wall with neutral mirror silicon (or something like this) it makes the room look much bigger.

@sarahleavydesigns The tiles are a little over halfway so only the waist and above would be visible You are right about the walls not being dead straight, I have found this out already. I think a glazier is the way to go. Thank you.

@smartypantsnancy looks great!