Anyone with proof of a UK address can apply for a Readers Ticket which will get them access to the reading rooms. The British Library's Business and IP Centre offers a range of electronic resources that will are useful in researching companies or industries.They may also have print copies of Market Research reports that they can consult.
A list of the available business and IP databases can be viewed here. Please note in order to make use of them you must visit in person. Also strict downloading or printing limitations may be in place. These limitations will have been imposed by the database vendors as part of the terms of the license.
There are a number of smaller Business & IP Centres in other major UK cities. The services on offer may vary from centre to centre, but most seem to offer access to at least some databases. Further information can be found here.