Brake cleaner in cans supposedly has at the very least a 6 year shelf life if stored correctly, so if you get through it a bit you may as well go for the 12 cans using the PICK20OFF code and it works out at £17.99, or £1.49 each per 600ml can.
And if you REALLY use a lot of it then 24 cans works out at around £1.29 per 600ml can.
That's pretty damn good, bearing in mind they sell singles for a minimum £5.20, and upwards.