Ciao
The Costa course was run at their roastery in Lambeth. It actually started with a tour of the roastery. Probably listed under Whitbread (the parent company).
I can't find a contact phone number on the website either. I should fill in the online enquiry form or call your local and ask for the head office address. We rung up and they just gave us the dates of the next public courses. It was £50 per head.
I have some input about Thomas Polti Which I'll take to the Members area!