sphil, I wondered the motivation issue myself. I don't think that the ABA principles of reinforcement and rewards are a no-no, whatever you try to teach, I am teaching DS piano very very slowly using colours, prompting and reinforcement - it's slow but we make progress!
But whether you should try to motivate speech with rewards is another thing, I also have my doubts about this which is why I'm dabbling with RDI & floortime. Dr Blank asked me why I want my son to speak. So that he can tell me what he wants or needs, I said. You already know what he wants, she said - which is true, I do, by interpreting his many non-verbal cues. But he needs to be able to be understood by other in order to be independent, so I guess that's why we try to encourage them (our kids) to speak. The goal of this programme, apparently, is to teach the child the language of others so that he is no longer an alien in the world - and for me that is a lot more important than how much DS speaks. The way I see it, if he understands language, 'cracks the code', he can be taught about the world around him. There is only so much that imitation and simple label language can teach. But if he can read a book about, I don't know, insects, that's pretty cool!
oh crap, late for OT session but I agree about South Hams - my friends in London with careers and lives rave about the Maldives or what not, but just take me to a beach in South Devon and I'm happy, thank you very much...