Paul,
Welcome.....loads of good gen here and generally quite friendly.
In answer to your question....Yes I have done the DBS Test. I passed and yes it is worth it, as you can then send a CV to the TOCS, some of whom may well get back to you. The TOCs most definately do reconise the pass and this pass will take a lot of pressure off you in any future applications.
Hope that helps.
Lanc