Currently I don't want to enable location services. I can drop the PUBLISH requests but first I'd like to under stand the reason for the loop.

> The looping happens when the domain in the R-URI is pointing to same server, but it is not listed as local domain for kamailio. You have to add it as alias or use it with domain module.
>
> For adding it as alias, add:
>
> alias=kamailio.marrold.co.uk

This is already in the original configuration I posted.

The capture the traffic on the server and paste it to the mailing list to see routing addresses:

ngrep -d any -qt -W byline "sip" port 5060

Cheers,
Daniel