paul wrote:

Hi I have tried searching for bleaching but I seem to be getting
conflicting information on the subject,

Where did you look and what did it tell you?

There are several sorts of wood bleach. Most work differently, on
different things, and have little effect on the others. Specifically,
oxalic acid is the one that's effective on darkened (aged or
weatherbeaten) oak or to remove iron stain from it, hydrogen peroxide
is the two part commercial "wood blech" that's used to lighten
tropicals or cherry, and hypochlorite bleaches (kitchen cleaners aisle)
are the ones for stripping off dyes or ink spills.

None of these are ideal for invisibly removing oil from oak. Much of
what you're seeing here is the optical effect of filling wood grain
with a translucent oil, not a dye per se.

I have made some kitchen cabinets fronm english oak but when I oiled
them with raw linseed oil they went quite a brown colour

That's just the timber darkening as you oil it. You shouldn't have used
linseed oil because in 6 months time it will be a bilious yellow colour
too. Nor should you have used raw linseed, rather than a boiled
linseed, as it's hard to cure it.


I have now sanded this off

You're unlikely to fully sand off an oil finish, it's likely to either
remain blotchy or to involve removing a lot of timber. Now you're using
oil I'd stick with it, despite any darkening. Faffing about trying to
change it will just make things worse.


As you've discovered, there's an old adage for finishing, "If you don't
experiment on scrap first, then you're experimenting on the real
thing".

You've built cabinets in what's basically a darker timber. Either live
with it, rebuild them in maple, or learn a lot about finishing first
before trying to change them. Fiddling will not help.