I have found
www.luckymodel.com to be excellent both with stock and price, and they have free post. Their site is a bit hard to navigate but if you type in Griffon then scroll through the Griffon range you will come across the brass tube.
As far as small copper wire, strip any type of electrical cable and you will find all different sizes of copper wire, the cables used for computers, printers, phones, rechargers all contain very small wire, the smallest I have found is 0.07mm which is tiny. A lot of these IT cables can be picked up at the two dollar shops and contain enough wire to last you a life time.
Des.