on a 1999 car i would say thats a massive amount of welding, it shouldnt really need any at that age:jaw-dropping.
have you seen the areas in question and has the car actually failed the mot?
if your not sure then i would get a second opinion.
bushes are a regular mot fail on e36/46 so quite common and relitively inexpensive to replace
E46 subframe tears aren't un-heard of. It's a little unusual on a 1.8 as it normally affects the larger engined cars.
Sounds like it may have had a hard life, the bushes were going which put stress on the already weaker-than-it-should-be subframe/floor mounting and then it's torn it.