Given the duration and intensity of cross races, you're probably best off with a normal base layer, short sleeve Jersey and arm warmers when it's cold.
In wet races it's better to have dry, warm clothes to change into after.
It was the wetter stuff I was thinking about.....
I was probably pushed that way because of yesterday's weather reminding me of the last time I rode up York's Hill and nearly drowned. And it was "only 40 quid".
Racing? Cross?