Beddington Farm being a landfill site is only accessable to keyholders. The site used to be open but 2 guys came to a sticky end on the site and Thames Water / Viridor erected fences to prevent a re occurance.
The Beddington Farm Bird Group have keys which are limited in number and normally become available when someone stops watching / moves away from the site. (It took me two years to get mine).
The Bird Group arranges tours which are advertised on Johnny Allan's website
www.diporglory.co.uk. The Croydon branch of the RSPB also take groups around the site. The next tour is on 22nd July.
There are several vantage points along the public footpath from Mile Road Bridge down to 100 Acre near Mitcham Golf course. The vegitation is growing rapidly and the public viewpoint onto the Main lake can be obscured at this time of year. Once the breeding season finishes work will begin to improve viewing from the path.
Having said that myself and the other members of the group do take people onto the site from time to time. I have got to know a few of the regular watchers including Paul (Paulwfromtheden).
I am always willing to assist regular non keyholders particularly if there is a rarity on site.
Photographers like to "shoot" the Tree Sparrows and have been given access to do so in the past.
I would certainly recommend one of the tours as an initial step. I do not lead tours myself, but will assist Derek or Nick to make a tour as enjoyable as possible for people attending.
I hope this information is useful and maybe I will meet you on a tour.
Regards
Kevin