into google, you will probably find a load of places. Had a place near me that used to have literally hundreds[possibly thousands] of old doors outside on the pavement, they stripped the old paint off them and flogged them; it was quite common for people to take stuff like bike frames in to be chucked in the hot tank.
Caustic dipping will remove paint and such but won't do much for corrosion.
You'd be better of getting it grit blasted to remove paint and rust. An alternative would be a dip in Phosphoric acid which neutralises rust and leaves a protective coating.
There's a place called Dip a quick strip in leeds as i keep seeing their van about, don't know if they do car parts though, there is also a place in york that does do cars and parts, no idea of a number mate but you should be able to google it.