You might want to contact TWI (The Welding Institute) in the UK because, I have'nt been current with British standards any longer so I could'nt confidently answer your query... I do know that most, if not all BS welding standards have been superceded by EN standards... Here's their website:
http://www.twi.co.uk/j32k/index.xtp

Here's a lnk with info on their standards:
http://www.twi.co.uk/j32k/unprotected/band_1/standard_index.html

Here's where you can purchase the standard you're looking for:
http://www.twi.co.uk/j32k/protected/band_13/faq_standardsorder.html

Here's the British version of our own forum only they're a bit more "rowdy" than ours at times and visa versa!!! Here's where you might get a good response with regards to your query:
http://www.ukwelder.com/

This one is the British Institute of Non Destructive Testing but, I do'nt know if it will help much:
http://www.bindt.org/

anywho, that's all I've got for now... I'll post if I find out anything new! ;)

Respectfully,
Henry

Generally speaking a BOP test is a Vickers hardness survey performed in the HAZ just under the weld of a single bead. This is a test aimed at producing the highest obtainable hardness that may be produced at a particular heat input.

Sorry, I don't know the max hardness value. It depends on the material being welded.

Best regards,

Mike