Lately it's been smelling strongly of mould. I've wiped the seals, washed the tray, unblocked the coin trap thingy (got out lots of grit & gunge from that). Have done the hottest wash (85 deg) & put through limescale remover. The upshot is that the whole kitchen now smells of mould.
Use Biological washing powder and less of it than they recommend. A few 90 degree washes too. It won't work immediately - the washing machine I inherited stank and it took nearly 3 weeks before I got rid of the smell.
dishwasher tablet straight into drum, hottest wash possible. Beware using bleach, had a nasty experience of it bubbling out of soap drawer and onto waiting dirty lothes! Take out you soap drawer and give it a scrub, you may also need to check there's nothing blocking the filter at the base of you machine (if you have one there of course..)
You can get very good descalers such as oust to maintain washing machines. The problem is caused by all the low temperature washes that we do now and it's recommended that you put the machine through a hot wash with nothing in it every six weeks or so to keep soap scum and mould at bay.
Using calgon or a cheaper alternative water softener in every wash stops limescale forming and extends the life of the machine