Just a quick question – do the full time employees have to also complete several hours of compulsory training in core hours?
You can’t easily have one rule for full time, and one for part time, without it appearing discriminatory, yet I’m guessing the trainer only works to company hours. It doesn’t really matter if it’s training, or selling widgits or whatever the actual job role is, its still working, ie time not at home, it’s compulsory attendance, which gives it the character of work, and it’s for the benefit of the company, not the employee, presumably at the company premises. It seems to me its just being asked to do something different to the usual.
You could try to meet them half way with time off in lieu, or requesting overtime.
It could be the training has to happen on a Thursday, as it’s say a paid or pre booked external course and your missus only works Tuesdays and Wednesdays, so some flexibility needs to be shown, but being told to turn up on the Thursday with no pay or expenses is not on. Even if she were happy with not being paid, who’s going to pay for childminders or what ever other things are usually done by her in the time they want her training?