bath tap

I have a Bristan Chrome Plated Quest Bath Shower Mixer tap and the cold tap seem to be pitting and the base appears melted or oxidised. any one ever seen this before. Tenant says it's occurred naturally. Anyone seen this before and why or how it may have occurred? What I do recall is that the...

Morning all, Very simple plumbing question but I'm getting lost in all the available fittings,etc. What Would be the easiest way to swap out the taps and pipe in this setup for a new tap, flexi hose with valve?