I'm sure you've already seen this but as it could probably do with being in this thread anyway, these are all the fares:
Adult
Cash Single: £4.30
Cash Return: £8.60
Discounted Single: £3.20
Discounted Return: £6.40
Oyster Pay as You Go: £3.20
Child (5-15)
Cash Single: £2.20
Cash Return: £4.40...