Setting up UCD as follows.

External RAD device on local 270 (don't want to use VM ports) Verified that calling 270 gets RAD message.

Hunt 3:601 Terminal Record contains 270. Verified that dialing 601 gets RAD message.

Hunt 4:602 Terminal Agent contains only local 350. Verified that dialing 602 gets local 350 if it's not busy. Problem is, it gets a busy signal if 350 is in use.

Incoming trunks are all tenant 1

Form 19 Call rerouting table for Tenant 1 has UCD/Att recording Day, N1, N2 all set to 601 and UCD on hold time-out all set to 602.

Incoming trunks all COS40 and 41 and my local COS23 all have on hold timeout set to 1 minute.

Feature 38 has a UCD login access code set.

Incoming trunks COS40 and COS41 and and my local COS23 all have option 301 Campon enabled.

Incoming trunk 106 has 602 set as Day, N1, N2 answer point. To direct the calls from this trunk only to local 350 via hunt 602. All other trunks go to reception.

I'm using my notes from our old SX200light to set this up on our new ICP and as far as I can tell, when 350 is busy, another call from trunk 106 or my local should get the recorded message repeatedly at one minute intervals till 350 is free. Instead, as stated above, it gets a busy signal unless 350 is free. Any hints?

In the trunk's COS, make sure camp on (#301) is enabled, to allow the trunk to camp on to the busy group.
If you try testing internally, by dialing 602, remember that you'll hear busy tone for 30 seconds, even tgough you're camped on to the group!
By the way, with UCD, you'll only hear the recording once.

For UCD if all members busy the Group concidered to be busy as well unless you specified Overflow point. Overflow in your case should be 602 recording Group.

You should be able to camp on to group if all members are busy

OK, I got this figured out and to be honest, I'm not sure at the moment, where the problem was.

I did notice that local 350 was a different tenant and so I changed that from tenant 3 to tenant 1 (I'll deal with the fallout from that when it arrives) and the other thing is that I realize that as I'm using a superset 430 set up as a sub-attendant, it asks me if I want to wait when camping on.

Thanks all for the help.

Look at your tenant interconnection table to make sure that Tenant 1 wasn't restricted from talking to tenant 3 - if it was there was probably a reason for them to be in different tenant groups. I used to use that type of thing all the time to stop toll free numbers ringing into the switchboard from being transfered to guest rooms.