<p>Since the majority of Oxford students take a “Year out” between (high) school and univeristy, you wouldn’t be much older than them. A year at most and that doesn’t really matter considering 40% are grad students (so over 21) at Oxford anyway. No-one would know anyway.</p>
<p>Most US undergrads here have done one year at a US college. However “most” really means about 20 in total, as there aren’t very may US undergrads (but about 700 grads I think. Lots and lots). </p>
<p>You are correct that you would have to apply to start agin in the first year (really not uncommon in the UK as this is what people do here in order to “transfer”. Start again).</p>