As far as I can tell, this is the full gamut of discount codes available, along with approximate probabilities:
- £1 off a £20 spend (60% chance)
- £2 off a £25 spend (20% chance)
- £3 off a £30 spend (10% chance)
- £5 off a £35 spend (5% chance)
- £10 off a £50 spend (2.5% chance)
- £20 off a £100 chance (2.5% chance)