I used these guys in Kettering Dean....
http://www.automaticgearbox.co.uk/
when I had a leak from the drive shaft at rear of transmission on my D2 S8. They did a 'transmission service' as well (which is basically a fluid change) and I was very happy with their work. They're very used to ZF boxes looking at the array of vehicles parked up outside and in the workshop. They were recommended to me by my local garage.
Just another option.