Back in the day I worked for a credit card company - the way scoring works is that you give a risk rating to the credit history (no 2 lenders will do this the same, although they all use either Experian or Cfas for the base data), they will also look at how often you move about (the less you move the more easily traceable you are) and other risk factors - having children in school, being married, being older, in full time employment (but not self employed), owning your own house, owning a car (your whereabouts can be traced through the DVLA) are all seen as good risk factors. Higher education and having a pension plan also improves your risk - you are seen as a person who plans for the future and therefore more likely to pay back debt.
The storecard company I worked for would like to see some evidence of late payment (but no current arrears) as it would mean that there was money to be made from interest payments - otherwise they would just be doing very cheap loans that cost the company more than they made. Therefore if you paid off your bank card every month in full and swapped to 0% cc you were unlikely to get credit with the company.
An ideal customer was someone on an average wage, who owned their home, car, had a good education and 2 primary school aged kids. We would like to see a monthly outstanding balance on any loans and that they had been on the electoral register for a while. A slightly unusual name scored better than Smith or Jones. It was an outright no if there were active CCJs, IVAs, the mortgage had arrears or late payment or if the outgoings were higher than income.