Photography Licensing Fee - No permission!

Hi. I've just found out that an image of ours (I run an entertainment company) has been used for a campaign by another company without any permission. The campaign has a print circulation of over 150,000 brochures (the full front cover) nationwide (UK) plus online usage on socials and website.

They have owned up and apologised and asked what the fee is we are looking for for the use of the photo. I have no idea to be honest, so am just seeking any advice for a rough figure.

Many thanks