I've recently started using 30 Seconds 1L Shower Cleaner and have found it really great. You don't need to scrub. Spray it on and leave it to do its work. You can then rinse it off later. For the initial clean, you might also like to grab some Selleys 750ml Rapid Mould Killer Remover. Make sure you open up all the windows for ventilation.
For the walls, I like to use some Sugar soap and magic erasers to remove mould growth. I then follow this up with a spray mixture of 1 part clove oil to 9 parts water. This kills the spores and prevents the mould from coming back very well. Personally, I've found the clove oil stops the re-growth of mould for longer than bleach does. It's also less potent on the nose.
After you have finished cleaning, consider the reason why the shower was so mouldy. Perhaps it just hadn't been cleaned in years, but if there is no exhaust fan, it would be worth installing one. Since a bathroom is a high humidity environment, it encourages mould to grow. The more ventilated the space is, the less likely mould growth will set in.