Is it safe to use a duvet under a sheet, instead of travel cot mattress?

[Babybear1]

Going away on holiday with DD who's 13 mons. She'll be sleeping in travel cot for 2 weeks, looked at the mattress in mothercare & it seems like a lot of money for what seems to be a layer od padding. Has anyone put a single duvet on top of orginal travel cot mattress & then stook a sheet on top? do you think it's safe to do so. Have a new 3.5 tog single duvet. Or should I just fork out the £30 for travel mattress

What about a folded bath towel?

Just not sure if that will be comfy enough, 2 weeks I feel is a long time?

Depends on the travel cot. I've done this with a travel cot & it was fine but my lo was older. £30 is a lot for a mattress.

I did it with my 16 month old when we had to live with mil as long as the sheet is tucked in it is fine

Thanks for advice, will give the bath towel a go.