TrimStab
I would be very surprised if 'The Friends', as you call them, got involved. It's not their line. Any backhanders are likely to have been paid by the defence equipment company through local consultants hired specifically for their contacts with key individuals in the host country's procurement system.
In days gone by, any UK goverment input to such activities was likely to be handled by International Military Sales (IMS), a quasi government department with offices in Soho Square.
...don't know what happens now.