How effective are vaccines against the Delta variant really?

There seem to be many different figures flying around for the effectiveness of various vaccines against various variants of the COVID-19 virus. It's hard to get a clear picture.

According to The Guardian, a source that I trust, there seem to be three main British studies:

• Public Health Scotland says that two doses of the Pfizer/BioNTech vaccine is 92% effective against the Alpha (British) variant and 79% effective against the Delta (Indian) variant. Two doses of the AstraZeneca/Oxford vaccine, on the other hand, is only 73% effective against the Alpha variant and 60% effective against the Delta variant.
• Public Health England says that the Pfizer/BioNTech vaccine is 93.4% effective against the Alpha (British) variant and 88% effective against the Delta (Indian) variant, while the AstraZeneca/Oxford vaccine is 66% effective against the Alpha variant and 60% effective against the Delta variant.
• Another, more recent, study by Public Health England concluded that the Pfizer/BioNTech vaccine is 88% effective against the Delta variant, compared to 67% for the AstraZeneca/Oxford vaccine.

There are some minor discrepancies here, but the general view is the same: Pfizer is very good, AstraZeneca just good. Moderna's results are likely to be in the same ballpark as Pfizer, and Johnson & Johnson/Janssen is likely to be similar to AstraZeneca. All appear to be very good in guarding against hospitalization and death from the virus (the figures above relate to the likelihood of catching, and potentially re-transmitting, it)  In all cases, a single dose is not very effective at all (Public Health England suggests as low as 33%) against the Delta variant, which is now establishing itself as the dominant one, and is the main one we need to be worrying about.

The jury is still out on whether it is advisable for people who have had a first dose of AstraZeneca to get a second dose of one of the mRNA vaccines, although the odds are looking good that this would be preferable to a second AstraZeneca dose, in terms of efficacy at least (NACI is now advising that a second mRNA dose is preferred for those who got a first AstraZeneca jab). That ship has already sailed for me, but I'm still happy to have had two doses, even if they were both AstraZeneca. (The only silver lining might be that some studies are showing that AstraZeneca creates a better T-cell response than mRNA vaccines, thus potentially giving better long-term protection).