Hi, Britain; Two 'like' people, separated by a common language. Love that line (from Gen. George S Patton). Anyway......back to the Rio.....The term you used...squealing...to me sounds like a loose fan(serpentine) belt. Have a helper try starting the engine while you are watching the pulleys that the belt drives. I've seen belts rust to pulleys, before. No, oil is not going to drain away from the pistons. Yes, the lifters could drain, but will refill as soon as the engine starts. DO NOT overfill the crankcase with oil.
Yes, the starter 'could' be making what I would call a groaning sound when low on voltage. Of course, while your helper is trying to start the engine, listen to the starter, also. A long handled screwdriver with the handle held to an ear makes an excellent stethoscope. (just be careful that it doesn't interfere with any moving parts while listening).
This has nothing to do with your immediate problem, but, if you haven't done so yet, replace the timing belt ASAP. Should have been done at 50,000 miles and can cause catastrophic engine damage if it breaks while driving.