In the end, I gave CQWW a miss today (because of my voice) and stayed on 10m JT65.
I keep forgetting that the UK clocks went back last night (we are now GMT until the end of March) and that it will be dark an hour earlier tonight. So, I have to remember that any DX on 10m is likely to peak an hour earlier. So far, just a single Brazilian spotted on 10m JT65 today. With the earlier darkness, it is less likely there will be many (or any) more today. I think the chances of USA spots on 10m has passed for today. I guess this needs a lower K index and a higher sunspot number, although I am no expert.
UPDATE 1536z: I have just spotted a station in Faro, Portugal, CT4RC (1814km) on 10m JT65 at 1528z, although no further South Americans. If the South Americans are coming through by TEP, then the Portuguese station indicates some chance of linking into this TEP from the UK.
See https://en.wikipedia.org/wiki/TV_and_FM_DX#Transequatorial_propagation_.28TEP.29 . This article is about FM and TV DXing, but it gives some insight into TEP.
UPDATE 1725z: In the last 15 minutes 2 more Brazilians (Sao Paulo area) have been spotted on 10m JT65. This is consistent with TEP and an extension to northern Europe by some other mode of propagation.
UPDATE 1800z: Now 5 South American spotted on 10m JT65 with the best RX DX being CX3BA (11131km) in Uruguay. I am more convinced than ever that this is TEP with extension to northern Europe.
UPDATE 1925z: No further South Americans in the last 3/4 hour. In the end 9 South Americans spotted with best DX on RX Argentina. I am wondering if we are seeing TEP extended by southern hemisphere Es? I doubt we'll see more South American spots tonight on 10m JT65.