Sounds like you have the COS option set to look for CLI on the analogue lines. This shows as a lengthy delay before the phones will actually start ringing on the handsets.
If you turn off the CLI options in the COS for the trunks they will ring straight away
Dialing out with ARS is no different to isdn2 or 30
Give the trunks numbers, put them in a trunk grp, assign trunk group to route, assign digits dialed to route
use digit modes to remove the 9 (uk)
Hope this points you in right direction