Moth or butterfly?

its beautiful

I say moth :)

Moth :o)

Butterfly.....it has plain antenna. I always thought moths had sort of feathery antenna.

I found your moth online:
Brimstone Moth
Opisthograptis luteolata
Here's a link:
http://www.mothcount.brc.ac.uk/moth_popup.aspx?SpeciesID=8

In general I think that most moths do have feathery antennae, but not always.
Here's another link to a website that I thought all those from the UK would like:

http://piccies.flybywire.org.uk/ButterfliesMoths/BySpecies-BritishMoths.html