I have just used the following number from the unverified entries database:

East London Textiles Ltd
0845 271 4989
020 8501 0743
ELT collector for charity no.1119024 Little Tresures (sic) Children's Trust

Pressing option 6 (other) got me through to the right place and someone phoned me back (from the CLI, I didn't have to give them the number) to arrange collection of a bag for Leukaemia & Lymphoma Research, charity no. 216032. No doubt they handle collections for various other charities as well.

The 020 number appears on the home page for East London Textiles, http://www.east-london-textiles.com