Hobilars/MtSgt are as fast as mailed knights, so pony doesn't do anything.
Fast pony is a bit faster than the early cavalry.

I'd place infantry only at the flanks for the English as Longbows have stakes which will pierce any incoming cavalry if you place them properly. That way only infantry can charge your front and your cavalry is quick enough to deal with them. No need thus to have infantry block your archer's sights and lower their effectiveness. Besides, longbows pack a punch in melee anyway.

As English, I usually go for general + 4 hobilars + 2 mailed + 8 longbow + 2 spear. Works fine generally and is fairly versatile. If you can hide 2-4 of your cavalry during battle, it will force the AI to attack your position, making your stakes quite useful even in attacks. Actually funny how you can exploit the AI this way.