How to get to Hilbre
Take the metro train from Liverpool to West Kirby. Walk along Dee Lane past the supermarket to the sea. You should see a notice board. This will give you all the information you will need to cross to Hilbre safely.
You must not cross to Hilbre island directly, you will encounter channels and mudbanks. Walk to Little Eye (aka The Eye) first. Do not attempt to walk across the Dee estuary to Wales. At Little Eye turn to the right and walk first to Middle Hilbre (aka Little Hilbre and Middle Eye) and then Hilbre itself. The 3 islands are in line, Little Eye is tiny and Hilbre is the biggest. There are many rock pools, but it is probably better to wait to explore these on your return journey.
You can stay on an island while the tide comes in and goes out again. You can buy your provisions in the supermarket on your way to the beach. If you have binoculars or a telescope you can see the birdlife or the seals. The seals can be seen on sandbanks far away at low tide, and at high tide they come in close to the northern end of Hilbre. If there is a group of you, you are supposed to obtain a permit first, if you're going to the main island.
I got to the beach about mid day. High tide was about 3 pm, and I stayed on Middle Hilbre. I had the island to myself and I dozed on the thick grass, which was as soft as a matress. At about 5.30 pm I saw people walking back to the mainland, if I'd waited half an hour more I wouldn't have got my feet wet.
It takes six hours to do what I did. You can find out high tides from the local Liverpool newspaper, there seems to be little difference in tide times. You can leave West Kirby at 3 hours after high tide, and return 3 hours before the next high tide. If you want to stay on the island while the tide is in, you must leave West Kirby at least 3 hours before the next high tide.
The Illustrated Portrait of Wirral by Kenneth Burnley will tell you more about it.
detailed information about Hilbre can be obtained here, including a map of the area