On education in the UCAS form, where you add your qualifications, there's separate boxes for modules. You can use as many as you need (e.g. if you do 2 history modules, then you fill in 2 module boxes putting the name of the module and the marks.) Hope that's clear enough.
If you got 90%+ in any of your modules, though, you should get these explicitly mentioned in the reference.
Edit: Was too slow, listen to the above!
Edit2: I think you can only put the unit grade in, not the ums number, as you've found.