The mattress arrived by next day delivery as promised. I unwrapped it & left it for 24 hours as advised, & it plumped up to 18cm as described. The mattress feels completely different to a sprung mattress but we had a good 1st  night's sleep. Two weeks on & we both feel it's the most comfortable mattress we've ever had. We both wake up without aches & pains & fully rested. All that & fabulous value for money too.