Looks like a denuded (hairless) Andrena cineraria, a solitary bee which is usually black and grey in appearance. If so would I be correct in assuming that it was taken much earlier in the year?
See images on the Bees, Wasps and Ants Recording Society (BWARS) here: http://bwars.com/Andrena_cineraria.htm
I would say probably Andrena pilipes. This nests July-August (2nd generation)
It's a scarce bee so it would be worth sending record details, including pic, to BWARS: http://www.bwars.com/Contact_BWARS.htm
Melecta albifrons is a spring-flying bee, like its host Anthophora plumipes. Flight period March-June. Any M. albifrons in August would be very unusual, very old and very tatty, (if still alive!) - you certainly wouldn't find 5 at once! I'm pretty certain this is Andrena pilipes, which, as I said, IS at Rainham (I live locally and see it there regularly) and will be found in reasonable numbers in July/August. Compare it with the photo on the BWARS website:
It's an all black bee with noticeable white hairs on the hind tibiae of the female. This species is large for an Andrena. Melecta albifrons typically has white patches on the upper surface of the mid tibiae, although these are not obvious in the dark form. Both very pretty bees that I'm always pleased to see!
Sorry Lynette, we seem to be at slightly cross-purposes! Your photo posted to the BWARS group does have a look of Melecta about it, but Chris's above is much more like A. pilipes (the tibial hairs really are distinctly different from those on Melecta - I've checked all my specimens), so we could well be looking at 2 different bees that are superficially similar in the field, being roughly the same size. It just shows the pitfalls in trying to identify bees from photos! If you had the actual specimen, you could take it to the Angela Marmont Centre at the museum to compare it with the relevant species in their synoptic collection. I've had a quick look through the BWARS database (I'm on the committee) and there do seem to be a couple of records of Melecta albifrons in August, but they are unusual. If you look at the Essex Field Club website you can see the county distribution of both species and read a bit more about them. Peter Harvey manages the website and it was he who first showed Andrena pilipes to me at Rainham several years ago. You also find a lot of them at East Tilbury.
Best wishes, Claudia