hi trippy.
i use a tfr called multi wash from auto glym.
this stuff is amazing, i,ve used it on the most oiled up engine you can imagine and it brings it up like new.
you cant buy it off the shelf, you need to find the guy with the auto glym van who delivers to the local garages.
it costs £39 for 25 lts and its biodegradable and is pet and flower friendly.
if you dont know how to find the auto glym guy let me know and i,ll see if my mate can find your local rep.