Rehearsal aids for this term's madrigals are all available free of charge on John Fletcher Music. Click on a piece, and then on 'MP3' next to your voice part to play it.
Since Robin Hood (SAT/B) p256 - this is a different website, as it is not available on John's site. Again, click the MP3 next to your part, in the 'emphasized' column on the left (under the Original Key Edition.)
O Magnum Mysterium
The Gjeilo piece is also on John Fletcher Music, but, being in copyright, it is not free. You would need to register for a subscription - £4 for 4 months or £10 for a year. Probably not worth signing up just for this, but if you sing with other choirs it can be very useful.