Corrosion - Inner seal has gone, help!

[Beautifulbodywork]

The garage I use recently fixed water coming into my 1984 Mercedes 230CE by taking the headlining out from under the sunroof and renewing rotten tray. Water had been gathering in the mornings in the footwells front and back drivers side. That problem is now solved but in the process of stripping out all the carpet the garage I use in Fulham noticed corrosion to low side inside all along sidebar which is carpeted where seat belt is. The garage has put down duck tape over the corroded area but I've been told it will only be good till next MOT and if I emergency stop the corroded area will snap off including seat belt. The garage say the inner seal has gone and to repair would be costly. Can anyone suggest a place I can get it fixed, not too expensively?
I want to keep the car but this is very worrying.

 

[Beautifulbodywork]

Corrosion, Inner seal has gone, help!

The corrosion is not visible from under the car under a ramp just at the side when the carpet is lifted off. Grateful for ANY suggestions!

 

[Mercedes 190E]

It is your inner sill that has rotted through, probably on the join between the sill and floorpan. It will be severely weakening the seatbelt and makes the car illegal to drive, in my opinion. (And probably also the Police's!) It would be VERY expensive to have the whole inner and outer sill structure replaced completely-probably far more than the car is worth, but that doesnt mean that it cannot be properly repaired instead. Find a local type garage or bodyshop (Not a Merc specialist!) and get them to take a look. It may be perfectly possible for them to cut out the rotten area and repair it locally with new steel which would give you as much strength as the original. It could then be wax injected to prevent further corrosion.

 

[television]

Have to agree with Mercedes 190E that you find a specialist welder who know how to do these things. the fuel and brake lines that pass under the sill could pose problems, but they will know about how to deal with those