I would like a list or a website of all colleges/institutions that
offer an evening plumbing course in London.  It needs to be the
qualification in order to become a plumber from scratch.  I believe
that is NVQ 2/3, but I am not 100% sure.

hi lisa,
 
"Floodlight is the official guide to courses in London. That's all the
part-time and full-time courses run by government-funded colleges,
universities and adult education centres in all the London boroughs."
http://www.floodlight.co.uk
 
The following link will take you to the list of courses you require:
http://www.floodlight.co.uk/cgi/new/database2/db.cgi?db=14&Subject=Plumbing&Geo=&Days=evening&termcode=&Cou=nvq&view_records=1&x=33&y=1
 
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Search strategy:
Went to http://www.floodlight.co.uk/
Entered "plumbing" in search box
Then clicked on "plumbing"
Selected "Anywhere" for location
Selected "Evening Courses" for Days & Times
Selected "Any term" for term
Entered "NVQ" in keyword search
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I hope this answers your question. If you need "clarification", please
ask me before rating the answer.
thanks.
--JB