This has been an interesting thread and it's a shame that parts of it have deteriorated into argument rather than debate. I'm sure there have been rude comments elsewhere about people who claim benefits, but two wrongs don't make a right.
Personally, I don't think high or middle earners should receive housing or any benefit. It should all be means tested. It's not needed and just makes one more thing we have to pay for. This country is in trouble: we have too few people paying for too many. This is not a criticism of people who need help, or in fact of anyone receiving benefits, just a statement of the fact that there are less and less people working and paying tax, supporting a larger population than ever before. This trend is likely to continue and we are seeing another manifestation of the problem in the pension crisis.
I have sympathy with people who will struggle on SMP, but if SMP is not enough, the answer isn't to top up through child benefit, it's to address the problem by increasing SMP. Or much better, for employers to prioritise maternity pay as a benefit, in the same way some offer private health care schemes. I appreciate, however, this is problematic for smaller businesses.
We all make our choices in life. Having children is a choice and not a right. Having a house with a big mortgage is a choice and while it's not easily changed, it is possible to downsize or move to a cheaper area in most cases. There are often compelling reasons why people don't want to do so, but that doesn't mean the rest of us should subsidise that choice. If a woman is the breadwinner, there is the option now of her partner taking a proportion of the parental leave and receiving SMP.
I don't agree with the "higher earners put in the most, so they should get something back" argument. We all get something back from the taxes we pay: we use the NHS, we have our rubbish collected, we have an army to defend us. More than that we get to be part of a society where (mostly, unless the system has failed) people don't have to beg on the streets and children can eat. If we want a society like that, some people have to pay for the rest, it's the only way it has a chance of working.