OK, no doubt you are competent to do the work, probably more so than some as you have years of experience.
The rules are (summarising)
If you extend an existing circuit you can do this work yourself without notification.
The biggest change with respect to you in the 17th is the use of RCDs on ring circuits. Any electrician who comes in to do the job and who self certifies that the work complies with the 17th will have to protect this additional bit of the circuit with RCDs.
Now, if you do the work, you don't have by law to follow the 17th, you need to make sure your work is 'safe'. Arguably following the 16th is reasonably safe. Who knows....
There again, if you are doing all this work in the loft, then you might as well change your CU while you are at it, and bring it up to the 17th. This would be notifiable work.
If I was you, I'd just notify the council, get some test equipment from work, and do it all yourself, including putting a new CU in. If you want to get up to 17th edition and have then 16th then you can do a one day course which covers the differences. The 17th regulations exam itself should not be much of a problem, you could probably pass it without knowing what an RCD is. Alas.
