Astromech Droid, R2-D2, White Dome, 30361c Body

Comes in 5 sets, made of 4 parts. The lowest-priced set it comes in is 7660 Naboo N-1 Starfighter and Vulture Droid (RRP £29.99).

Check the minifigures carefully when buying a used set: they're part of its grade.