Just wanted to add that my DCs' nanny (she lives in) is from Senegal (i.e. she's black) and my main bugbear with her is that she's too soft on DS1. So the whole idea that all West Africans are overly strict is wrong.
BUT, having lived in West Africa, I think it is true to say that there is a stronger propensity for families to use old fashioned methods of discipline** - rightly or wrongly - and certainly, corporal punishment is still used in many schools from what i have heard. In any case, you rarely see naughty children or hear tantrums.
** By that, I don't mean that kids are beaten to within an inch of their lives or anything like that.
I actually would not use race or nationality as a means to select childcare. There's good'uns and bad'uns in every country and that certainly includes this one. I had a laugh to myself when i read that someone would only used Slovak au pairs or something like that. My friend certainly wouldn't - hers ended up shagging her husband....
Perhaps, good English nannies are hard to find because any worth their salt are probably working for vast amounts of money in the States or Middle East, not the relative pittance they'd get here.
In essence, the aim of most au pairs is not to pursue a career in childcare but to secure themselves a place to live while they learn English/earn money to send to their families or whatever.
Anyway, good luck Kittywise, with finding yourself another nanny. You need it with 6 kids - don't know how you cope!