Hey Phil,
It's a long shot, but it might be worth reseating the
CPU. Those symptoms can occur if there is no
CPU present or detected. Memory and expansion card problems will always beep if a problem is detected.
These boards are not the easiest to get hold of, let alone looking for a cheap one, you may want to keep your eyes open on e-bay. Acer don't distribute their motherboard like ASUS and ABIT, they are normally made specifically for their machines, but you may be able to find a second hand one. I've seen some eledged new Acer motherboards around the net, so I may not have all the facts straight there. You'll need the details of your motherboard such as model number. You can use SIW:
SIW | Download should give you the details you need.
EDIT: Marked as Answered.