The t-shirts are XLarge:
Angels VS Silence and Faces of the Doctors ^.
On the website the measurements were length 28 1/2 inches and width 18 3/4 inches but I think they are a bit smaller than that.
I’d say they would suit a UK size 16 and US size 14. As this is a giveaway and I pay postage, you don’t really have anything to lose if they don’t fit.