Looking to replace my teenage daughter's mattress. She doesn't sleep well and I'm hopeful that a new and better mattress could make a difference to her sleep but she also needs a new mattress regardless - so it's not like I'm hoping for some magic. It's single bed. Where would you go to 'test' them? What are some good shops to go to and how do we decide what works? Budget not exactly unlimited but also not the main factor. Thanks.