I have stayed at Glenview many times and am always happy with the rooms and the service. The breakfast there is excellent!
The best room is room 2 - it is on the ground floor and has a large bathroom with a big roll top bath in there.
Mumbles itself is amazing. There are great bars and restaurants (I recommend Knights for food). The BEST ice cream sundeas can be found at Verdi's, and there are excellent walks all along the Gower Peninsula just waiting to be discovered.