I can recommend this Kilrock Mould Spray Cleaner.
I have used many times cleaning tiles and grout.
Ideal for cleaning grout when it starts going black or pink.
Spray on leave 20 mins then rinse and your done.
The last time i bought from Home-base it was £4.99.
so at £1.99 from Home bargains is a Bargain
Effectively removes stains caused by mould and algae
This professional formula has a bleaching action
Ideal for all interior surfaces