Save £500+ by using this fix!! Have patience and stick with it!!

Video 2:    • 2)V70 servo hissing repair fix broken...  

Replacement seal on eBay: https://rover.ebay.com/rover/0/0/0?mp...
Or type in: 03771850181 in eBay search....

Remember use silicon grease!! Plastic tools to release old seal / refit new seal.

Steps I carried out:
Order new seal as above or used servo from eBay etc making sure it's the same part number as yours (ideally fit new seal or might be doing the job again soon)
Once you have new / replacement seal.....
Disconnect battery
Remove driver's seat including electrical connectors
Remove plastic shroud lower dash under steering wheel for better access (a few torq screws I think), sorry didn't mention in vid as mine is permanently off the vehicle
Disconnect brake pedal from servo connecting rod
Disconnect steering shaft thing/connector!
Trim carpet for better access
Remove grey dust cover
Prise out old seal
Clean white cylinder
Lube white cylinder and new seal with silicone grease
Fit new seal and press in using plastic implement
Check this is properly installed
Replace grey dust cover
Reconnect steering shaft and brake pedal
Replace seat and all connectors
Connect battery
Job done

This is just how I did it, I'm a diyer not a pro, do the job at your own risk and above all good luck!!!!