Understanding Society User Support

I am writing with the hopes that someone can clarify precisely how income from benefits is constructed in the BHPS (and Understanding Society). In particular, I have been using wFIMNB (income from state benefits received in month before interview) in BHPS and w_inc7sben in Understand Society.

However, we would like to look at payments of specific benefits, such as state retirement, income support, and housing benefit. Am I correct in assuming that it is only possible to accurately identity the payment amount of individual benefit types if the survey respondent only reports one of them? Because otherwise, they are summed together in wFRVAL (w_FRVAL in USoc)? There is no separate variable containing the amount for each benefit type?

For example, if a person receives income support and a housing benefit, I will only know the summed amount of the two but cannot discern the separate amounts of each?

Any clarification on this point would be greatly appreciated.

Many thanks in advance!