Which solenoid to replace?

I have a fault with my solenoid, but when I search for it on line they do not look like mine. Can any one direct me to the right replacement?
Also does anyone know what the black block next to the solenoid is?
Thanks for any help you can give.
Mick

Attached Images

• IMG_5141.jpg (139.0 KB)
• IMG_5142.jpg (89.2 KB)

Which solenoid to replace?