saintly he can't imitate yet, but we are working on that too. We are using hand on hand prompts to teach him the signs.
sassy I think biscuit could well be the first sign ds does unprompted! 
dudesmummy we are in the same position except not much guiding in fact not much requesting of any sort. Difficult isn't it.
signandsmile so lovely and encouraging to hear how it's helped your ds.
ineedalife. Great to hear your experiences too, like the "good talking" suggestion.
madwoman will look at "owl", haven't heard of it but sounds like it could be useful. Will also look to incorporate singing and signing as he really loves us singing to him.
Alyswho. Thanks for your words of encouragement, I know it's just a different path, but an unknown one to us at them moment. I think once I see that all the things we are trying are helping him in some way, I'll feel less useless and more confident in our decisions.
Adamsapple it's lovely to hear your experiences and I think you're right, signing is going to help ds so much, need to stop beig fixating on him speaking but focus on him being able to communicate in general. Always thought he'd speak by school age and hopefully he still might. It's the balance of remaining positive but not expecting or fixating...or something along those lines.
chocjunkie, thats just the kind of thing I do, in fact I thought I might have written singing by mistake! :)
Thanks everyone :).