I have acquired an HPI truggy for free. I have got the nitro engine going no problem but cannot get the receiver to respond to the Transmitter. What is the problem please? I have tried a different receiver and transmitter but no luck! The servos for both steering and throttle seem ok. Any advice please?

You may need to bind the receiver to the transmitter. Which receiver and transmitter are you using?

Looks like the process for some HPI kits is to hold the 'setup' button on the receiver (may need a thin screwdriver or paperclip to do this) while turning on the power, releasing after a second when the light is flashing. After this, hold the bind button for on the transmitter until it lights up solid.

If this doesn't work you may have acquired the wrong transmitter for that receiver.