I've not read the whole 10 pages, but am going to chip in with my 10p worth...
Depending on the government to support you is risky, if not foolish, because you can be certain that the level of support available is going to reduce dramatically over the years. Whether the State should or shouldn't support you is a different argument altogether, but I would say ignore the people who tell you you have no right to a child unless you have money. Comparing wanting a fancy car but not being able to afford it to wanting a child is offensive, in my humble opinion anyway.
To me, the critical thing that leaps out of your OP, is the fact that you have decided you can never earn more than 14K or have a permanent job because you can't interview. That kind of defeatist attitude is not something you'd want to pass onto a child is it?! This is something you can get help with, easily. Libraries are full of books about interview techniques, career guidance, building self-esteem, self-development. Colleges have courses, free or very cheap, you can take for building self-confidence. Ask your agency to help you get a permanent position, they can give you mock interviews and feedback. Go to your GP, explain your problem and how much it's effecting your life and ask for counselling or Cognitive Behaviour Therapy. Having a child is such a huge commitment, surely you owe it to yourself to make the effort to try and improve yours and their chances in life? And even taking a child out of the equation, surely you just owe it to yourself?!
Go to evening classes to learn a new skill. Do some volunteering with an organisation that does something you're interested in. All this not only builds confidence, it also gives you stuff to talk about in interview, and you meet a wide range of different people and get to know them in an informal environment... and one day one of them may well have a job going and offer it to you without you even having an interview. And thinking about it now, short term agency work frequently leads onto permanent work doesn't it?! Without the need for an interview? If it doesn't happen in the industry you've been temping in, then ask your agency for help getting into a different industry. Yes, it's fucking difficult trying to improve your lot in life. It requires hard work, sacrifice, tenacity... but so does having a child.
30 isn't too old! Spending a year or two now focusing on whatever is holding you back and securing a permanent job would be time well spent. Then, proud of what you've accomplished and more secure in your earning power, start making a baby :)
And my last point...
You can't rely on the government to support you forever, not because it's morally wrong, but simply because in the future the support won't be there...