There are many companies that offer 'chocolate making courses' but actually simply show you how to temper chocolate and produce a few goodies. You won't actually make chocolate from the bean which is the correct interpretation of the phrase.
Making Chocolates in London
If you did want to have a good time producing truffles, ganaches, chocolate shapes and the like then you can't go too far wrong with the variety of courses run by Green and Blacks. Those courses primarily operate out of East London. As they've been doing them for many years you can expect them to be highly polished and run like clock-work.
Also The Melange offer parties and workshops in Peckham.
In the North
You can find courses run by Betties in Harrogate. These are great guys and are expert and producing wonderful chocolates. The costs are pretty pricey at £180 for a 7.5hr day. But you will learn a great deal.
York Cocoa House also run a range of chocolate events from the likes of their 'Drop in and make' sessions primarily aimed at children to masterclasses which are focused on those that may like to get into the chocolate making industry in the future.
In Manchester Slattery's have a fantastic variety of courses aimed at fun days to those that really want to push forward making chocolates for a living. I've had these courses recommended to me often.
Shires Cookery School offers both day and short courses in East Haddon, Northamptonshire.
The School of Artisan Food near Worksop have a very extensive list of chocolate-related courses aimed at people that want to work at the upper end of the chocolate sector.
Squires Kitchen has some courses for those who do want to make chocolate seriously.
Chocolate Delight has courses for team building events and hen parties in both London and Brighton.
In Chichester, you can find both workshops and chocolate related parties organised by Le Salon du Chocolat.
In Alresford and around the Hampshire area you can find Chocolate Craft, who does small and large chocolate-related events.
The award-winning William Curley has a range of events at his sophisticated boutique in Belgravia.
The Edinburgh New Town Cookery School have short courses about cooking with chocolate, not making chocolates.
The Edinburgh School of Food and Wine have evening classes about chocolate.
Cocoa Black have a very extensive range of courses catering for a wide variety of needs.