I recently sorted out a service on a local owners Rover 75 and found the sill problem on his car, i have passed on Tom's number to him, also the information that he can obtain the sill parts from Tom and get them welded on local if he wanted to.
Here are the photo of the said sills.
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You can see from this photo the jack support as been compromised.
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The above passed it's test in June 15/21 with Monitor and repair if necessary (advisories)
Nearside Rear Outer Vehicle structure is corroded but structural rigidity is not significantly reduced (6.1.1 (c) (i))
Offside Rear Outer Vehicle structure is corroded but structural rigidity is not significantly reduced (6.1.1 (c) (i))