I use LS NepalExt, OlyMons and LS Nuptses, all size 47, all fit well. Have tried on Spantiks but not used.
It seems generally people need to size their Spantiks a size or half up from other LS boots, but you currently seem to doing the opposite? If your toes are touching the front, in any boot, then they are too small/short, particularly if you plan on doing any frontpointing, or walking downhill. From what you say your OlyMons 45 fit well (lucky if you get no heel lift!) and I have found (I have two pairs of OlyMons) that the liners do pack down a little, but not nearly as much as some other liners (Millet Everest etc). And of course the newer LS liners can be heat-moulded, though I have not tried that, I just left my OlyMons liners as is.
So are you thinking of trying Spantik 45.5? That might give you more toe room and would be in line with others' experiences vs. OlyMons. If your foot fits well into both Scarpa and LS boots then you are lucky. Many Scarpa wearers find LS too narrow. I fit LS well, but find Scarpa too short for their width (47 is too short, 48 rarely exists).
You might also want to check out the relationship between LS liner and shell sizes. They don't increase evenly. It's several years since I bought mine so I can't remember exactly, but it was something like a 46.5 and a 47 might share the same shell but different liners, or vice versa. This was a common practice for manufacturers of double boots, and could affect fit quite a bit, depending exactly on your foot. Not sure if it applies to Scarpa, Millet etc.