200tdi windscreen pillar rot

Just bought a 92 200tdi 5dr (to go with our trusty 300tdi). It's had all the usual suspects, boot floor, sills, inner wings done properly and Waxoiled ... engine and transmission are good, and electrics all seem good. Problems exist however in the base of the nearside screen pillar: there has been a horrible great wodge of filler bunged in and I get a feeling that's responsable for the wet carpet on the passeger side. The old girl gas plenty of life left in her so I wonder if anybody has welded this area and has any idea how difficult/expensive it is?
Depending, I may have to get someone in the East London area to do it or I may have a shot myself.

id be wondering whats under the rest of the waxoyl

Well, I had a bloody good poke about ... having had a well tin-worm infested 300tdi and knowing where to look (everywhere)... and it seems to genuinely had all the lower body stuff done (got the reciepts for the welding). Course I know there will surely be lurking nasties in the odd place.