measure the units first! alot of older units would be in imperial measurements,( i now we went metric in the seventies but i still meet people who use feet and inches). where you can get caught out is with the wall units that are 610mm high (24") whereas the nearest std door is 570mm. also check the widths of the doors. you'll find some of the larger doors not to be 595mm, which is the std now, but to be 575mm which you wont get. Yes you can cut the doors down but if you go for high gloss doors they are only mdf inside so the difficulty is in re-edging them with a matching edging. if you cut down soilid doors make sure you leave enough on the stile (door side) so as to re bore for hinges.kitchen door std heights are 570mm 710mm and 900mm high widths are 295,345,395,445,495,595. ward robe heights are mostly 2250 high though you can get doors 2275high in Softline in cherry orchard and the pannelling ctr do some of their ranges at 2150mm high the widths would be the same as for the kitchens. most times its more economical to change the wall units. another thing to consider is if you change the colour of the doors you may have to change the blend panels and kickers as well to match