Well spotted pluggy, (thought for a second id used the wrong dil on the plans!!!)
Here is a brake down of how much the components would cost from there (but you could salvage most of them from old electronics)
1x Atmel ATMega168 = £2.65
1x Stipboard = 72p
1x 7805 Voltage regulator = 26p
2x LEDs = 16p
2x 220 Ohm resistors = 8p
1x 10k Ohm resistor = 4p
2x 10 uF capacitors = 12p
1x 16 MHz clock crystal = 45p
2x 22 pF capacitors = 10p
2x .1 mfd capacitors = 10p
1x small momentary button = 18p
Total = £5.94
Optional extras
Header Strip = 26p (for 36)
Single Row Sockets = 56p (for 25)
28-pin DIL sockets = 16p
PP3 Battery Clip = 15p
