From my own personal experience (and having both my parents with their DNA on Ancestry as well), I have found it to be broadly representative. But that is just a way of saying that it is quite vague.
For example, "West Midlands" appears to cover from Sheffield in the north down to Gloucester in the south and from Shrewsbury in the west almost to Peterborough in the east (although it does specifically exclude it on the map, stopping at Castor and Marholm - for context, Castor is about 2 miles from Peterborough).
Others have said that Bristol also seems to come under the West Midlands as well.
"What percentage is just sort of noise?"
This is just my personal opinion, but the 1% - 3% are likely just noise. For example, Ancestry claims that I have 3% Northwestern Germany, 2% Netherlands, 2% Norway and 2% Sweden.
But, both my parents also have their DNA on Ancestry and they have none of these (although both my parents do have 2% Denmark which I don't - but it's vaguely near Norway, Sweden and Northwestern Germany!)
But I think that there is likely quite a difference between arguing about Norway, Sweden or Denmark on the one hand and Benin & Togo on the other hand.
That total of 6% from West Africa could likely be quite accurate.