Firstly why this talk of 100 grain bullets ?
Unless the OP is planning to take it to Scotland for large deer (where it might rightly be viewed askance), he may use the bullets for which it is optimised, e.g. 70-80 grains.
But if the primary purpose is to shoot deer (fallow or other), why settle for the absolute bare minimum legal calibre ?
In the UK the .243 is a crossover calibre. Its just about the maximum that will be authorised for fox alone, and it is the legal bare minimum for large deer.
Yes it is effective with suitable ammo and a well placed shot, but on the occasion when I had the opportunity of a large deer (not expected, we were set up with the .243 for small deer), my guide was emphatic that I must be absolutely sure of my shot placement. On subsequent outings we used a 30-06 and I think both of us felt much more confident.
As it happened I later took my first roebuck and and a muntjac with the 30-06, and I was impressed with the performance. Very clean kills, but with far less meat damage than the .243 used to create.
If the OP has the option to choose a larger calibre I think he should take it, nevermind the hassle. .270, .308 or 30-06 would be the obvious candidates.