Any one have any advice on the best material for kitchen unit doors. Solid wood (say oak), a wood veneer or laminated MDF (I assume this is what the oak style, maple style etc doors are made from) Could the steam get into the veneer and laminate and weaken the glue?
In a direct answer to your question, solid wood is the best but most expensive.
On the other hand you only get what you pay for. I have a Sematic laminate kitchen from Germany, it's about 20 years old now and as good as the day I installed it.
Under normal kitchen use there would be no problems with any material, but you must never boil a kettle under a wall unit for example, this would cause no end of trouble, the steam would ruin any surface.
It depends on what style/appearance you want. If you want it to look like wood, then only solid wood looks right (IMHO). Clean-line styles of white and numerous pastel colours are obviously laminate. And you get what you pay for in terms of appearance. You will perhaps have spotted that much of the cost (50%) of a Unit is accounted for by the doors
I don't think you need worry about steam getting in - only where a unit has been subject to continuous immersion in water over many hours have I seen this happen. And then its often with the carcase, say from a dripping water pipe inside the cupboard.
Sorry Buildersmate I disagree with your opinion re steam. I have seen wall units and there doors ruined by steam. All down to kettles being boiled under the units. I have also come across a unit that was badly damaged by a steam cooker.