Redout, you cannot do two ratings at once. That would be double charging the hours. 1 hour of training has to be towards one rating, what ever it may be.
CY, you can do MEP rating as part of your CPL (a license not a rating) and have the skills test count as both. Usually costs about £1.5k more than a SEP CPL. So you save around £500 with normal UK prices. This is what most do.
However, you can get the MEP on your PPL and just transfer it onto your CPL when you get it.
You have been given some duff info. Do it if you want.
EK