Rafaela,
The combined BHPS and UKHLS cohort is so far spanning three censuses, 1991, 2001 and 2011. To enable linkage with external small-area datasets (incl. the censuses) we provide a range of area unit identifiers to the end user. Due data confidentiality restrictions sub-regional area identifiers are only released under Special License (SL) agreements or made available via the Secure Data Access (SDA) portal.
BHPS datasets are provided with geographical look-up tables to Lower Layer Super Output Areas (LSOA), Census 2001 Area Statistics Wards, and Census 1991 Wards (http://www.esds.ac.uk/findingData/bhpsSL.asp). UKHLS datasets with LSOA and Census 2001 Area Statistics Wards (http://www.esds.ac.uk/findingData/ukhlsSL.asp). Ordnance Survey postcode grid references are accessible via SDA for both BHPS (http://www.esds.ac.uk/findingData/bhpsSDS.asp) and UKHLS (http://www.esds.ac.uk/findingData/ukhlsSDS.asp).
To convert data from one set of boundaries to another, UK researchers can use the GeoConvert service (http://geoconvert.mimas.ac.uk/index.htm). The output files are weighted proportionally to the number of residential addresses at postcode level found in the target area units. To apply any other weighting users would have to create their own GIS (see e.g. areal interpolation chapter in http://www.spatialanalysisonline.com/).
To link data from Census 1991 and 2001 to a BHPS/UKHLS dataset, I would, first, get the data of interest from Census 1991. I would convert/re-aggregate the observations into LSOA using the GeoConvert service. I would then get the data from Census 2001 and 2011* at the same level of aggregation and, finally, I would apply for a SL agreement to access BHPS/UKHLS look-up tables to LSOA. This is only an example and you might have to revise according to the exact data you are after.
Do let us know if you have any other questions.
Jakob
*) Expected to be available from Nov 2012
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