A very noisy silence!!

"Silent night" I think not!! We recently purchased a bed with a Silent night Miracoil 3 mattress. Within a few weeks it started to creak when my husband got out of bed. It then got saggier and saggier on his side and started making horrific creaking and boinging noises if he so much as turned over in the night. Eventually if he even moved position the mattress noises woke me up! We tried to turn the mattress around so that I had the broken side but this just meant that I had back pain all the time and the other side gave way too.
My husband emailed Tesco direct to complain and to their credit we were immediately offered a replacement of superior quality, the Ravel. However we have now had this for a fortnight and it is already creaking and groaning every time my husband moves (he is under 16 stone so by todays standards, a lightweight). My advice would be if you want a silent night buy a mattress from some one else!!