Annabel karmel food flasks

Just wondering if anyone out there has got one of these Annabel Karmel food flasks you can take your puree's out in to keep them hot??

I shelled out £12 for this flask and took it out for the first time today and it was rubbish - the food was barely lukewarm and this was 1.5 hours after I made it piping hot! (meant to keep hot for 5 hours).

It doesn't seem broken, but I can't understand it.

I've chucked the instructions away now but thought it said something about trying to warm the inside first, so I did put boiling water in it for a while before I tipped away then loaded it with food.

I've chucked the recepit too so taking it back will be tricky, anyone else had any probs with them or have I got a duff one do you think?

Thanks
Love N & Isla (10 months) xxx