Research SME businesses to identify those that develop software in house

I am looking for someone that is able to do some research into identifying SME companies in the UK that have the develop software in house.

I am looking to identify these companies as they would be potential clients for my software testing services company.

I plan to use this research to target my future marketing to the companies.

The focus would be on companies in the south east of England.

It would also be helpful to know if these companies also have software testing capabilities in house.