hi ds1 used to be cow's milk and soya intolerant and we have some gluten sensitive people in the family too so I have been through this. there's a yoghurt alternative called 'rice and rice' made in Italy I think which our local healthfood shop stocks. Very sweet though, so I tended to make my own set custard thing with rice milk eggs sugar and cornflour and sometimes with flavouring. Or just do homemade pots of fruit/ fruit puree.
I have successfully made gluten free bread with the Doves Farm gf bread flour and rice milk. I use slightly more oil and less rice milk than suggested on the packet.
i would avoid soya lecithin as well, at least at first.
The M&S fair trade dark chocolate bar I bought the other day was free from all the things you're avoiding.
Plamil tends to use soya as a milk substitute, but I thought some of their bars used pea protein instead. However I've just been looking on their website and I can't find that information so I either imagined it or they have changed the ingredients.
We used to eat lots of rice cakes. And the best spread I found was Pure with sunflower - the yellow tubs not the organic blue ones as they have soya in them.
And instead of looking for cheese substitutes we ate loads of hoummous! Strangely ds1 can't stand hoummous now.
better go as ds3 is waking up