I have been experimenting for a home made shower cleaner to use in between the big clean and this one seems to work the best.
In a large spray bottle (I used a litre size) add the following:
1 Cup white vinegar
2 Tablespoons of any type dishwasher rinse agent
Fill the remainder of the bottle with water, distilled or filtered if the water in your area is hard.
Spray on and leave to clean.