Is this an outer sill?

[Shinnster]

Hi all, sorry if this a stupid one but I have some welding to get done on my van and probably need to source the parts myself.
what is this rusty hole section underneath the sliding door? is it an outersill? and if so, would i need to buy this part? https://www.justkampers.com/sliding-doo ... -1992.html
if it isnt that, what would the section be called? many thanks in advance!

and then the next thing would be anyone know a garage / welder close to West London area to get the repair done?
It cant be driven on the road so need to hire a flatbed to get it moved there, hence why it needs to be close to my area.

[Aidan]

that's the one, take a look on brickwerks there are two repair panels available depending on exactly what is needed

[Shinnster]

thanks for the swift reply!
I need left and right so will have a look on brickwerks!