I'm not criticising you for posting it mobaholic, and I know people keep mentioning these from time to time, but I view it as a bit unnecessary, redundant or anachronistic.
I've even had a disagreement with someone who thinks he needs to add this to a giffgaff wiki, but I reckon it's a voyage too far into nerdery, and its effect will be somewhere between neutral or it might confuse people and put them off, risking making them think why on earth do I need to remember and use all these
Basically, using the call divert menu in all modern phones automatically compiles and sends these codes anyway.
I did hesitate before posting, as you can see from my OP, but I reasoned that the USSD codes included some which are certainly not available on any of my mobile handsets - for example setting the delay before a call forward.
I appreciate that your smartphone may be better than mine, but the list is of use as a resource for reference surely.