Two rising mains why? Do I need them.

[anythoughtswelcomed]

So my DH who works in the building industry but is not an actual qualified plumber, he has moved our kitchen sink and fitted a water softener least he is trying too! The mains come in through our kitchen wall goes to the kitchen tap and out to the downstairs bathroom and the pipes go towards our new boiler fitted by a moron gas safe registered boiler (who we complained to gas safe about because he wasn't gas safe and is now being put through some sort of disciplinary for trying to kill us so I wouldnt the trust a word he says). My DH has connected the cold water pipes that run to the softener but when he tried to connect the hot water pipe that comes from the boiler he discovered he hadn't turned the water off when he turned the mains off does that make sense, it seems the boiler (a Valiant combi) is on a separate water main. The boiler is 2 metres from the kitchen rising main but the walls of the house are local stone and 2 2/2 foot so all pipe work work bends round door opening etc. Needless to say the plumber didn't comment on this when he fitted the boiler, he was too busy ignoring lethal gas pressure drops.
My house is 500 years old the boiler/downstairs/upstairs bathroom is in an extension which was probably built in the 70's both are at the back of the house.
Why do we have two rising mains? Do we need them? I was told recently by another local plumber (im not very trusting of plumbers any more) that we have the highest water pressure in the UK. My DH has no idea where the section nd rising main enters our house. My DH says we'll have to get a gas safe plumber to connect the boiler to the rising main that comes in the kitchen.