Tiling above a slightly slopping bath

[PerpetualLeakingRoof]

I plan on tiling above the bath this weekend but last weekend while I was laying out for the tiles I discovered that the long edge of the bath might not be perfectly level. It's pretty close, no more than 5mm out over the 1800mm length, but we're using 100x200mm tiles with a bevelled edge and I'm concerned even this small error will be obvious.

The way I see it I have three choices...

1) Just tile up from the side of the bath accepting that the tiles will be very slightly out of level. I don't think there's any chance you'd be able to see it's not perfectly level.
2) Tile bag on level and cut the tiles at the bath. I think this will stick out like a sore thumb as the bevel on the tile will shrink.
3) Tile bang on level and just use a thick bead of silicone to fill the 5mm gap at one end. Might have the same visual problem as No 2 though.

The bath is already as level as I could get it so I don't think trying to alter that now is going to improve the situation. I suspect that at least some of the inaccuracy I'm seeing is just down to the difficultly of measuring from the slightly curved edge of the bath.

 

[matlob]

I'd do 2 but cut the bevel off all tiles so it's not so obvious. This would give you a bit thicker edge when meeting the bath too. You wouldn't notice the 5mm over 1800mm that way.

 

[PerpetualLeakingRoof]

I should have said there's a slight step up (about 70mm) at the head of the bath. If I cut the tiles on the long edge I'll end up with an awkward grout line and thin bits of tile along the head end. Perhaps I should just bite the bullet and accept that I've got a lot of cuts to do.

No, you know what, I should just use the top of the step at the head end as my level and cut as you suggest. Don't know why I didn't think of that earlier. Thanks.