Thank you so much for taking the time to give me a detailed response. I have a couple more questions for clarification and next steps.
Based on what you have said, what I would like to get out of Voxalot is:
1) use all the ENUM options available for me so I get maximum free calls. I assume I just route all calls (except those that I want to use PSTN) to Voxalot and then set up a dial plan that routes the unmatched ENUM numbers through Engin.
2) Overcome the issue where Engin wont accept inbound SIP calls to my number. So what is the configuration approach I should take to overcome this?
Have you actually done this and got it to work? I tried to do it 'quickly' last weekend and the whole thing stopped working. Just want to check before I do it again.