As Slaphead says, oxallic acid will do the job well. I got mine from Boots (special order) for about £5. Be very careful when handling as it is very toxic; wear gloves and watch for splashes.
A useful trick is to mix it with wall paper paste to make it gloopy to stick to vertical surfaces. Roll/brush on, leave for a few minutes and then hose off....made a great job of my (ahem) sailing boat
Thanks for that. Did you need to polish afterwards? Does it attack gelcoat?
Y10 is oxalic acid based and as it's a gel it sticks to surfaces straight out of the tin.
Cillit Bang works great on barnacles and calcium based deposits (I've just cleaned the hull with it) but it doesn't get rid of tough staining that has permeated the gel coat. Give it a go first though, as it's only £2
Auto Sol. Comes in a metal 'toothpaste' tube, about £3 from any auto factors shop.
just put it on with a toothbrush or cloth and polish off.
It brings the console and moulding up treat and takes out any stains and is ideal on the stainless of course...