http://www.licencebypost.com/
They run a BCAR distance learning course but only for BCAR as yet. And time is running out for the good old section L.
Apart from that CSE at Oxford run 3-4 week courses. Brunel might or Brooklands in Southall.
On another note, as long as your AD300 is at the CAA, you can still sit section L papers in June. Sad misguided A & C friend is taking his Electrics in June, earliest date available !! Hope this helps