some tips from a well known immigration site
# Owing to the sophistication of forgers, your attachments should be originals.
# We are now recommending that a photocopy be included with every original.
# When submitting original bank statements, the sort code and account number can be blackened out in order to prevent identity theft; this information can be given separately.
# When submitting original salary slips, the National Insurance Number can be blackened out in order to prevent identity theft; this information can be given separately.
# It is perfectly acceptable to give the applicant a sealed envelop with all your attachments inside. Mark the envelop "CONFIDENTIAL DOCUMENTS: To be opened by the ECO". And include a self-addressed envelop so they can be sent back to you.
# Don't overdo it with photographs and mementos
# If you opt to include email or chat transcripts, be VERY careful about what they contain
