Be careful what fare basis you fly.

The information I've found (for BA's OneWorld partners I care about) is that British Airways Executive Club credits flights in following fare categories:
American Y, B, G, H, I, K, M, N, O, Q, R, V, A, W, X, Z
Iberia Y, M
Cathay W, B, Y, H, M, V, T, K in coach; J, C, D, I in business
Canadian B, G, H, K, M, N, O, P, Q, V, X, Y, Z

So it looks like you can't count on using deep discount fares on Iberia for the 100,000 mile bonus.