The past two MOTs at different garages have both had this advisory:

 

'Offside rear (inner sill) suspension component mounting prescribed area is corroded but not considered excessive'

 

If it has gotten to this stage already is the shell already terminal - as in, once it's set in, it can't be corrected without welding?

 

What I mean is, would it be best to get the area to bare metal and re-paint/underseal, or just rust-convert and underseal?

Get as much rust off as possible, especially the flakey stuff and treat it with a rust converter and then prime it straight away. (after about 15 minutes) Then use underseal or a stone chip paint. I have used a garage on an estate in Portslade for 15 years and although they have failed my Mk2 many times on a MOT it never has been on anything major.

 

Regards

Phil

Thanks - out with the Aquasteel then