Landlord deposit return, what are my rights?

Short and simple, we did an Etat de Lieux as we were moving out and the landlord signed off saying that everything was fine.
Two hours later tey called us to say that the “reconsidered” and will only return half, we were tired and trying to move back to England in the middle of Corona so my gf said ok.
When we got the deposit there wer 40 euros missing and he had another bogus excuse.
Im my eyes, we were being nice by saying ok to half after they said and signed that everything was ok and the 40 euro missing ahs angered me.

Do I have the right/ would I be wrong in now demanding the full amount? i.e. the other half plus 40euro?

How much are we talking about?

Hi @ptf
He has withheld 430 euros (half+ 40)

Do you have a signed copy of the etat de lieu? If so, send him/her a stiffly worded letter by registered post. Here is a model:

Hi @JJones,
We have the picture of it that he sent to us.