Best to do the *entire* floor before you start with any units. This
way things like washing machines will be more easily removed for
service etc and without risk of damage to the floor.

Assuming, of course, that the floor covering is reasonably cheap and easy to
fit (such as the OP's vinyl). If it is expensive or labourious, such as
stone or slate, then it might be a prohibitively expensive option. My floor
area would go up by around 60% if I went under the cupboards. I do, however,
intend to raise the floor where appliances go, to solve the problem of
extracting them.

Christian.