I ve been offered a westfield nosecone, bonett, and scuttle the parts are all 10 years old but in good condition. What sort of price should I look to pay for them

As little as you think you can. Do you know what he/she wants for them at all? Also depends if they're a matching set or scratched/chipped at all.

are they for a pre-lit or modern westy?

If modern they don't fit without some fiddling. The 'tub' or bottom part of the bodywork is larger than the frame, ie sticks out, the nose bonnet etc, sit on the tub so you'll have to pad out your chassis to make it fit.

If it is the modern one, it does take a little fiddling, as said but not too bad, I have loads of photo's if you need them
Rescued attachment Front Shocks.jpg

The panels are 10 years old but all in failry good condition some scratches on the nose cone underneath nothing serious. Scuttle includes screen though glass is cracked.