Thanks for your advice guys. Job done with 40mm main run, 1 stand pipe at end of run from dshwshr in 32mm and a connection into sink waste from wmc. All tested and ok. Many thanks. Ian S.
Is it acceptable to have a main run of 38mm waste pipe to the outside drain then connect 32mm wastes from dishwasher, washing m/c and sink unit into the 38mm pipe? This is to save running three separate pipes through the outside wall.