L322 Front diff rebuild/replacement

Hi, my second post. My son's L322 4.2SC Petrol is making a continuous grumbling, grating, whine from the front diff. My mechanic suspects that the pinion bearing is going. Bit urgent as it's been getting louder so fear it will fail soon. I see from previous posts that removing and replacing the diff isn't too onerous. Can anyone recommend a company who can either remove and rebuild the existing diff or supply and fit a replacement. Or even just supply a replacement and I can get my mechanic to fit. We are in London. Thanks in advance

Forgot to say it's a late 2007 car

I've used Winchester Gears many times, always quality work. https://www.winchestergears.com/range-rover-2002-2012-61-c.asp

Thanks, reached out to them. Do they supply on an exchange basis?

Yes, the details are on the website.