Second degree loans and parent learning allowance

I am looking at doing a second degree in an Allied Healthcare professional which I understand means I would be eligable for funding.
The degree I currently hold is Plan 1.
In terms of paying back, do I calculate Plan 1 Plan 2 rates on top of each other, or would I just pay at Plan 1 rate that will end up paying back both loans once I reach the earning threshold? (To clarify, are the two percentages added together or it is just Plan 1?)

Also, as a parent to a young child, am I eligable for the Parent's Learning allowance if I already have a degree?

Thank you