I'll just add a few words here having been through all the official routes with Mrs WHBM being from overseas.

Firstly ignore those comments from those in the USA speaking about "attorneys". Attorneys do not exist in the UK.

Secondly, nothing to do with your wife, you need the right documentation yourself for working in the UK, which every company HR department will check on day 1. It is not your wife who will be doing the job, it is you. Even British people starting at many companies have to show their passports nowadays, because that's what the procedure is, and you would certainly be expected to do so, with all the right visas, if you were obviously from overseas. So you need to get this, otherwise what is the point in coming. You will apply for this visa at the British High Commission in South Africa.

The reason why people started going through Ireland is that there are no border controls between the two countries, and never have been (the "Common Travel Area"). The Irish immigration authorities are just as straightforward in identifying people without the right docuentation as those in the UK; in fact people who are from somewhere like Africa who arrive in Dublin directly from overseas without good cause (eg tourist around Europe) are unusual, and stick out even more to them.

An ancestral visa (for those who don't know, a visa to "come back" to Britain from Commonwealth countries if parents/grandparents were British) does allow the family to come with you, as long as you can support them. As I understand it, it is only your wife who qualifies for this, and being pregnant, and also having a medical complication, she is obviously in no position to fully support you all ( a family of four, soon to be five) financially. Some of us here will be wondering what you are doing choosing to leave your wife for another continent at such a time.