I think I've just found my mistake. There were four winning single bets with the three horses, the ticket states 1/4 the odds for a place.

1) £1 win at 5/1 = £5

    £1 place at 5/4 (1/4 the odds) = £1.25

2) £1 place at 4/1 (1/4 the odds) = £4

3) £1 place at 4/1 (1/4 the odds) = £4

Making a total of £14.25

I forgot you get the stake returned so I should have added another £1 to each of them making an extra £4. It makes a considerable difference for the treble because you have to add the stake to each leg hence the large discrepancy. So I'm better off than I thought, think I'll have another go tomorrow.