I've just used [broken link removed] in a seriously DISGUSTING shower in a house I've just bought and it is nothing short of miraculous. The grouting was virtually solid black... I had to steel myself just to open the door! I sprayed this stuff on and I could literally see the gunk disappearing in front of my eyes as I worked round the cubicle. (I sound like an ad!)
I got it in Atlantic Homecare on the Clonshaugh Road - cost around €15-20 for a 500ml bottle but well worth it. (Was inspired by the Atlantic coupon that came with my ESB bill.)
They had a separate shower cleaner which I didn't try, because for bad mould (which this was), the box recommended the Mould Spray. Would definitely recommend for a first clean of something gross - something gentler would probably suffice for day to day maintenance. They had a whole row of Hagesan products, sue ellen, so though I didn't notice the grout sealer mentioned above I'll certainly be going back to look for it. If it's anywhere near as good as the mould spray it'd be well worth getting.
One thing... The link I used for the picture mentions using it for silicone, but as far as I remember, the bottle said it could stain silicone. (Don't have it in front of me at the moment.) But for grouting it was brilliant.