What should I wear to a spa (corporate do for a few hours)?

[MrsFogi]

I've been invited to a spa evening (Cowshed in case of relevance). I have never been to a spa - what does one wear and does it make any difference that it is a corporate evening (so a company has invited a number of clients (including me ) but I only know one lady who has invited me.

I assume you'll be in a robe, so a swimsuit for underneath. They'll provide the robe and slippers. Take the swimsuit with you and get changed there. Minimal, if any make up as it will sweat/ wash off. Take a hair scrunchie type thing if you've got long hair. Take your own flip flops if towelling slippers give you the Heebies ( they do me).
Have a lovely time!

Thanks LadyOTC, so pleased I will be able to cover up, I suspect I will need to do some heavy duty maintenance the week before !