​White vinegar is all you need.

​viakal is the best out therr

it's brilliant for cleaning (especially the spray) but for your kettle I'd agree with mittromney that white vinegar is best - I felt I had to rinse the kettle out a lot to get rid of the viakal smell but vinegar rinsed out much more easily and it's cheaper.

Yes, it's effective. Several applications may be needed depending on old and thick the limescale is. One application is all you need to remove a light coating of limescale. At the end of the day it gets the job done.

I think it's brilliant, careful not to leave it on too long as one of my taps got a slight corrosion mark ( I had forgotten about it so was on for 30 mins+). But several short applications very good. I use on weekly basis and keeps taps looking new

Yes it's the real deal. I use the squirty bottle version but presumably the spray bottle is the same. Shifts nasty deposits and leaves it looking very shiny. My other favourite cleaner is liquid soda crystals which I use if no limescale deposit. A great old fashioned cleaner that does a stunning job, so much better than all the new stuff with fancy names.

​No. You must be confusing it 151. Easily done

Try Cillit Bang Limescale And Shine Cleaner - best I've ever found. Also, on offer for £1.75 @ Wilko at the moment.

Their other products.

​what cheap brand did your girlfriend buy? this is not available in poundland