Can anyone recommend a sofabed which works equally well as a sofa as a bed?

[extremelychocolateymilkroll]

Currently have a futon which used to be our bed - and worked great - but the mattress keeps slipping down. It's also too wide so have to use lots of cushions to enable you to touch the back of the sofa. But, because it's so wide and long it makes a good bed. Can anyone recommend one which serves both functions equally? TIA

We used to have one from M&S that was very comfortable as a bed and as a sofa
It was this one

Thanks blametheparents.