Paddy Roxburgh"]Iroko is very durable and naturally oily but is a real pain to work, the high silica content blunts blades very quick and it is very prone to tear out with alternating grain. This can be overcome when using hand tools with a sharp blade and a close set cap iron, or use of a scrapper. Be prepared to sharpen a lot. Sometimes the planner thicknesser can tear it to bits. Get your blades freshly ground. I have read about people using a back bevel on their blades to give it a higher angle of attack but have no personal experience of this/
Meranti is much less problematic although does have reversing grain. It is however rather soft and gets dented quite easily. It is relatively durable and cheap. You can also commonly get it PAR which can save a lot of work.
You are right to worry about oak going black, but a good finish will prevent this.
What are your existing steel doors like. Are they constructed in a way that you can attach a 3/4"frame and panel to the inside with a layer of insulation in between. This is how I commonly do narrow boat doors and allows for a nice draft proof seal on the inside and the security of steel doors on the outside. This also means you can use oak faced ply for the panels making construction much easier. When I go to the dock tomorrow I'll see if I can post a picture of sone doors made like this with iroko frame and oak faced ply panels.
Paddy[
Thanks Paddy for your input I would love to see the photos when you get the chance,
I have thought about putting wooden panels in the steel doors as they are good and I could put a frame around them,But I did fancy the idea of double glazed units in wooden doors I thought this would give it better security than just glass and give us a view but not as good as steel doors, your right about working with iroko a tough one to work with Ive done some garden furniture from it Thanks for your help Martin.