" Having had two smallish Karchers fail due to the plastic pump housing
cracking I am looking for something more reliable -

Though this may not be the reason your washers failed, by far the biggest
reason for this type of failure is not draining them properly when storing
them away for the winter (usually in an unheated shed or garage)- the
remaining water freezes and expands thus cracking any casting. Just thought
this was worth mentioning for future reference.