I think he meant "Halon Replacement" i.e. FM200 rather than some "replacement Halon" fire extinguishers, which are illegal /forums/images/graemlins/blush.gif
I don't know if they stock what you are looking for, but I recently bought some new powder extinguishers for the boat from www.budget-fire.co.uk, and they were very competitive on price, and v quick delivery....