Cadbren.
So, the A&A Celtic foot are bigger than the cavalry? I bought some of the cavalry and as you say found them more akin in stature to the Foundry British Celts. I assumed the infantry would be similarly small and thus wouldn’t mix well with other newer ranges. If you confirm the infantry are bigger I will risk buying some given A&A’s current “buy 4 get 1 free” offer which makes them excellent value-for-money.
A&A infantry are very similar in size to Crusader. I don't have any pictures to hand but there are painted examples on the net which show mixed bases of the two companies and it's not possible to see which is which unless you know the specific poses and details. A&A tend to have scabbards on the left hip for example. The main difference is that the A&A metal is softer so more care is needed in handling weapons as they're more likely to bend.