There is no legal obligation upon any lottery organiser to publish the odds of winning. Indeed, with most lotteries it would be impossible to do so. For example, if your local church runs a raffle to support the appeal for repairing the church roof, they'll list the prizes as (for example) £50, £20, Bottle of Whisky, etc. They might hope to sell £500 worth of tickets but, if their fund-raising gets a lot of publicity, they might get £5000 in ticket sales (which will make a very big difference to the chances of winning).
The People's Postcode Lottery is based around the idea that there are 1.756 million different postcodes in the UK (although those in Northern Ireland need to be subtracted from that figure for the purposes of the lottery, as NI legislation prohibits the People's Postcode Lottery from operating there). However (as I understand it) only those where participants live are actually entered into the draw and the prizes are then distributed between participating residents within that postcode. (So if, for example, you're the only participant on a winning street, you get the whole prize. However if 3 other people on your street have entered you'll only get a quarter of it).
So it would seem impossible to give precise odds for winning a prize but it would still seem that the chances of your postcode coming up are actually very slim (simply because of how many different postcodes there actually are).
It's worth noting that only 25% of the revenue from the People's Postcode Lottery goes to good causes (as against 28% from the National Lottery)