i'll say from my experience more often than not, i am the same size for everything sans the few items like coats and sweaters since coats are usually coat on the large side and sweaters like the lambs wool. EFM sweaters are also TTS but size up if you plan on wearing with shirt underneath, or anything for that matter.
did you take same size for UU tshirts as your UU oxfords?
I sized up on the t shirts myself. Should get them sometime next week so maybe someone else has a better answer that has tried them.
I got the dark gray oxford now kind of wish I got the blue but wasn't sure on the sizing, if everything fits I will probably order a few more things. Hopefully they get a restock of the blouson in burgundy, also wanting the riders jacket in blue.