This is a very specific question to your market, in the UK but I will have a go at a more general form of the answer.
Many people are scared of change, especially people in larger organisations ... this is largely because they are focused on implementing the steps placed in front of them. They don't want to deviate from the course set in case it impacts their job security if they stick their neck out.
What you need to do is find the right people in these organisations, the ones who are defining the processes and guiding the companies, rather than those defending their position from all sides ... and then you need to pitch your concept in terms that make it appealing to them (specifically).
Maybe in your case you need
- Approach the Sales director/CEO and couch it in terms of "reduced cost per aquisition", "shorter cycle time", "Guaranteed X through the door per quarter"
- Approach their second best sales guy ... for a small percentage of your commission we can feed more into your basket putting you on top.
- To their direct smaller competition, we can help you compete against them.
Overall summary. Large companies aren't 1 entity, they are 1000s of individuals looking to either get to the next position or defend their current one ... you need to find the right person and tune your pitch to suit their situation.