In reply to pak.pako: The problem with ice screws and Scottish climbing is that you generally need none, sometimes need a couple but occasionally need lots.
At a rough guess:
For around 70-80% of routes you probably don't need any, you can find other gear.
For another 15-25% of routes 2-3 screws will be enough.
For perhaps 2-3% of routes 5-6 would be ideal.
However for a final 1% of routes were, depending on conditions, you may need two belays on ice screws you might need 8+ to be completely happy.
Most people work rounds this by only having a few and then relying on their partner also having some or borrowing some for specific routes or when climbing at specific venues like Ben Udlaidh.
For grade III I wouldn't be expecting to place many screws- unless climbing at somewhere like Udlaidh.
I've sometimes seen climbers carrying screws where they really aren't needed. If it's an icy route/ gully it will quite often say so in the route description. If it's a buttress climb it's unlikely screws will be of much use as there will usually be reasonable wires/ hexes/ slings you'd place in preference.