3810 as sip ua. CLI problem

Hi Guys, first time on this forum and you seem like a knowledgeable bunch so I’ll try you.
Have just connected a Cisco 3810 (this is a solution built to a low budget) to an ericsson MD110 pabx
via an E1 Qsig channel. Pupose is to integrate an existing sip network with the traditional voice network.
Router is running as a sip ua. All is pretty good so far, calls can be made in both directions, speech, ring etc OK. Only problem is CLI (calling line ID, I think ANI in the US) only works in one direction ie the pabx extension number is displayed as the calling line on the sip handset. Does’nt work the other way. The sip extension number is not being displayed on the pabx handset.
The Q931/voice ccapi debugs show both ANI and DNIS numbers so I’m inclined to think its a pabx setting thats the issue. I can’t find any specific router interface commands related to passing CLI across isdn/qsig E1’s. Anybody have any ideas at all? thanks