OK, 40th birthday party looming & have a v fitted clingy dress. Am Shredding like mad but would like a bit of extra help. Have read so many great reviews of Spanx but am balking at the £25-ish price tag. So my question is, are they worth paying 5 times as much for as ones I can get in Primark? Unfortunately I have nowhere locally I can try the Spanx on so can't compare - and the cheapest place online doesn't accept returns as they're underwear. Can anyone advise, if they're as wondrous as some people think I will swallow the cost - but are they?