Henna at hairdresser in London?

[Shadgal1]

I've a few greys and when I was pregnant I used Lush henna to colour my hair. I loved it and want to use it again but it was so messy and difficult to apply. Now I've a small baby to look after there's no way I can apply it myself and my OH would make such a mess of the bathroom and my face if he did it...

Lush used to apply it for you if you paid them a tenner but they don't anymore...

Do you know of any hairdressers in London that might do it?? I need to sort my hair out but don't want expensive chemical options...