Re: Any other way for water to get into oil apart from a cracked head/gasket??
not necessarily the headgasket.
that's what happened to me, and i assumed that it was a gasket, imagine my suprise when i pulled both heads off and could't see any damage. If your compression holds, it's not the headgasket. could be a cracked head, although it is more likely that intake manifold has corroded around the gasket and leaked water through.
have a look also at the timing chain cover, they seem to corrode around the water jacket, or behind the water pump. worse case scenario, although unlikely- a cracked block, but if the car runs smooth it's not, however it would explain high pressure in the cooling system.
Start off with the thing that takes the least amount of work, i.e timing chain cover....i, unfortunately didn't, and found myself with my whole engine in pieces before finding the fault.
oh....i've just realised that you said an EA, therefore it must be a six, i've a V8, and am unsure of the engine layout,but hopefuly you can make some sense of it.