I recently noticed one of my rear diff drive seals had started to leak. I intend to change the seal myself in the next few weeks. In the meant time, I thought I would check the level to make sure it had not got too low. When I took the plug out about 100ml of oil came out. As I understantood it, the oil is set using the plug hole so it seems strange it has been overfilled. Is this probally the reason my seal has started to leak? Anyone else had this issue?

Have you had any work done on the diff? When I had the diff bearing problem I had an oil leak later from the breather and the dealer said that they had put too much oil in. I think that 700ml was the required amount and no more. 3 x FL1 2 manual + 1 auto
5 x FL2 4 manual + 1 auto
Now Discovery Sport P250 MHEV SE

Have you checked the breather isn't blocked

I have only owned the car a few months. It does not look like it has had any work done on it recently. I could not get the breather pipe off top of the diff, I did use an old brake cable to poke down the pipe after figuring out which one it was. I could not be sure it had oil on it by the time I pulled it back out. Is the breather pipe robust enough for me to really pull on the pipe to get it off?

Marcmax - you are correct about filling

From the FL2 workshop manual:

CAUTION: Make sure the vehicle is on a flat level surface.
Raise and support the vehicle.
1.
No provision is made to fully drain the rear differential.
During repair procedures, fluid will be lost. A container
should be positioned to collect any spillage.
2.
Make sure the vehicle is level. Remove the rear differential filler
plug and discard the sealing washer.
3.
Fill the rear differential, until a thin thread of fluid runs from the
filler hole.
Refer to: Specifications (205-02 Rear Drive Axle/Differential,
Specifications).
4.
Using a new washer, install the drain plug.
Torque: 35 Nm
5.
6. Lower the vehicle. Jules

Thanks for the replies. I will replace the seal, check the breather and refil the oil as per the spec. Will monitor the oil level after that for a month or so and see what happens.