Tony,
Philip has reported my preferred oil remover, and Bugbear the same way. 
Some beech planes I leave with the hand and finger wear that have left the mark
of the user, but if they are as you describe, it is grungy, dirty mess, and I
just hate it.

Is the black only in the oil, or is it like a chemical reaction with the tannin?
I've done complete tool box sets of the "black oiled planes" consisting of
moulding planes, bench planes including plough planes and fillisters, by
removing the wedges and blades and splashing the surface with a generous amount
of metho, or if a complete set, soaking it all in a shallow tub of metho for
about 10 minutes.
I don't leave them in the soak for long. 
I take one out, and replace it with grungy one at the back of the queue
(line..paddy) I use a rotating group of about 3 or 4 pieces of fine or medium
grade steel wool soaking in the metho and shaking them about under the surface
removing the grunge until it's done. If there are more than 10 planes I will go
through quite a bit of the steel wool as it wears away. And replace the metho as
it gets real dirty and looses its oomph.
Now, if the black is a reaction stain like ammonia in oak, or acid of some sort,
or the wet iron contact ... you might try the oxalic acid. That can be got from
bunnies I think. (Borg, Paddy)
I've seen it used on oak with great results. 
Then you will need to oil or colour them with you favorite warm yellow finish. 
I'm not a fan of BLO. 
I've spent lots of time getting grungy, black sticky sh¥te off my Dad's and
Grandfather' stuff. Those things I really care about, and then there are the
tons of other tools swimming in it. The tools that pass through my hands look
un-saleable to me, so I give them the treatment too.
Pictures you ask?
Here we go...
The jointer at the back has the hand prints, and the front two are cleaned and
shellaced.
http://www.peterm
cbride.com/Maling/maling_tools1.jpg

Here is a cleaned set. 

http://www.pete
rmcbride.com/temp/images/moulding11.jpg

And here are some cleaned and shellaced and the rest not. 
http://www.petermcbride
.com/Maling/maling1.jpg

Regards,
Peter
In Main Ridge Vic
Australia. 



> On 1 Sep 2014, at 4:46 pm, "Tony Blanks"  wrote:
> 
> Friends,
> 
> I seek advice, guidance, experience or failing that, opinions, before I do
something I may come to regret.
> 
> I have some European (English) beech moulding planes, boxwood slipped, which
have been oiled within an inch of their life and then apparently stored in the
back of a chimney.  Dark doesn't begin to describe them.  I doubt that they will
ever be returned to the warm honey brown of patinated beech, but I'd like to
lighten the colour if that can be done short of using paint stripper.  I looked
at Tony Seo's Galoot Formula #1 page, but reading the cautions I doubt that
adding more linseed oil and wax to the existing coat will improve the situation.
> 
> Any suggestions as to how to go about doing this would be appreciated.
> 
> Thanks and Regards,
> 
> Tony…
..........