I visited earlier today, being on site late morning / early afternoon, and had no trouble finding decent numbers of the Southern Emerald Damsels present, both on the wing and settled on vegetation. At least four pairs in cop. were evident, perhaps a total of 15+ individuals being recorded.
The pond closest to the M40 is the one where the emeralds are, this however within the landfill site and therefore those visiting it trespassing. There's no doubt that this would give the best opportunities for encountering the emeralds but individuals were almost continuously to be found in / on the path-side vegetation immediately west / north-west of the pond / boundary fencing.
Parking's limited with space for three cars on the verge immediately west of the entrance to the recycling site, a lay-by a little further to the west, on the eastbound carriageway, allowing more parking but necessitating a longer walk to the site.
Take the footpath just west of the recycling site entrance south and follow this downhill, over a wooden bridge and past the pool on the right. Continue south until you reach the metal five-bar gate in to the landfill site / the copse. Follow the footpath around the western side of the copse and then scan the hedgerows etc. about the path on passing the obvious lone pine to the right of the path. The most northerly part of the pond can be seen poorly from the path, should you wish not to trespass. Patience along the path will get the damsels, they being seen regularly from at least early morning to early afternoon today.
The hedgerow bank on the right soon after entering the path area had showy Purple Hairstreak, the initial pond passed had smaller numbers of odonata, including Common Emerald Damselfly, but the largest numbers and variety of odonata were about the most southerly pool and adjacent scrub, dried grassland and thicker sedged / reedy areas; Pale Galingale also here.
A dozen species of odonata were seen, a dozen+ butterfly species and a few day-flying / disturbed moths, including Beautiful China-mark as well as numbers of both Red Kite and Buzzard overhead, Blackcap and Chiffchaff in the deeper scrub / hedgerow.
All the best if you head there, it's certainly worth it!