John, i had the same problem with a broken flange on the cat, and had the same reaction to the price. Like you, I had it re-welded and its fine so far (18 Months).
For future reference, i have since found the short cat available on ebay, around £134, (no idea how good they are) so if you are stuck, might be an idea to buy an extension and fit the short cat? These are used on the +8 I believe. (I also bought at the time a De-cat pipe so i could use the car if ever i had trouble finding a cat under £600)
Regards John K
