If you guys just want to do a Master's degree, do not mind the ranking of RAE since that is a ranking of research capacities (if you want to do doctor, then you need to consult www.rae.co.uk). I wonder if you people know the ranking of teaching quality, which is also an official ranking and if the teaching quality of a certain field is 24 (24 is full marke concerning teaching quality, library, staff, material etc.), then you need not worry about your choice.
Do mind the teaching quality, not research capacity of a department when you choose where to go if you just care about your Master's degree.