Hello Peter, and welcome.
For the dry mouth I found that whole milk worked quite well for eating.  A product called Biotene mouthwash works as a thicker and longer lasting effect in the mouth between meals.  I can't say if it is available in the UK but they have a web site   
www.laclede.com   They have a whole product line for dry mouth.  As to getting any salivia back, it seems everbody is different.  Some get none some get some.  It takes time though, I got just enough back that I can talk and get through the day without the water bottle constantly by my side.
As to your other questions I can't help you.  I didn't get chemo.  There may be others that will.
Good that you have made it through the tough part!