Martin wrote:
a deep rumbling noise...one that rumbles very nicely throughout most
of the house - particularly upstairs.

Pump bearing probably gone. They have a limited lifetime.
Normally they are easy to replace as there should be isolating valves either
side of it.
You may have to purchase/borrow a pump spanner along with the new pump.
Go for the beefiest pump you can afford, it will be worth it.
i.e. if yours is 5m head get a 6m one. It will be quieter for one thing.