SWMBO's Corsa 1.4 has just failed its MOT spectacularly on rust hole in front subframe

. Told by main dealers that it is not allowed to be welded (?) and a new subframe is about £500 retail (although I could get it trade) plus fitting. As it is a 2001 Elegance top of the range model, brought by us new and has now only got 49256 miles on it (backed up by all old MOT's and a full service history) and is in immaculate condition we are very sad about this.

Question is - are they correct that the subframe cannot be or is not allowed to be welded? If that is right then it is not economic to pay out circa £350 (trade) on a new subframe plus fitting costs as car is probably only worth about £400 - £500? with an MOT.
Could pick up a used subframe for about £60 - £100 on fleabay have it fitted for about £150 but there would be no real guarantee of its condition rust wise and thus next MOT could fail again.
Could easily get up to £500 by breaking it as 1.4 engines go for about £300-350, probably alloy wheels with good tyres £100, seats etc £75 plus other odds and sods, but am not in a position to SORN and store it to break it.
So it looks like its going to the crusher which is a great shame as it is in tip top nick apart from this subframe. We have been to see a Viva 1.0SL A/C this morning, 6 month old with 475 miles on clock and are going for this. Main dealer says that one of the grease monkeys races stock cars and banger at Arlington near Eastbourne and he may well use it for that if he wanted to.
That upset wifey who is/was very attached to her poor old Corsa.
If anyone on here wanted to collect it and take it on for repair to use for themselves or to break it for me, PM me, but will need quick reply as its going on the 28th.