There are so many different types of "mahogany" and if you want it to match then you will have to take the adjacent piece with you when you buy. You may well find the shipwright/carpenter in the yard/marina has bits of off cuts. If you are lucky enough to live in Poole area you can go to Howells in Cobbs Quay who have stacks of small pieces to choose from.
You can bet your mahogany door is'nt - real mahogany comes from (I think) Honduras and is simply no longer available - and is probably illegal even if available /forums/images/graemlins/shocked.gif
As Tranona says you are better to take a piece along if the look is critical since even if you specify iroko, African mahogany, meranti etc etc these are really just generic names for several different species of tropical hardwoods - usually quite poor quality.
When I liven in East Africa we got loads of really good hardwood that you never hear of in this country - Mninga, Afzelia, Pili-Pili, Muhuhu and so forth. All that makes it this length is the 'export quality' - the crap!
thanks, EC Bernie! Robbins were very helpful and not at all expensive (given the small bit required).
I am aware of the "variations" in "mohogany"... (raised by the other posters). Fortunately the piece required does not have to match perfectly (it is only for an inner batten which is not really too visible from the outside). I am sure it will do fine.
and, yes, Tigger, is not (yet) a classic piece of antiquarian fancy. But its joinery is not too crap either /forums/images/graemlins/mad.gif