Hi Baz,
I found myself in the same position as you after one day of STI ownership....so I know how you must be feeling. I researched all possible avenues - but decided that the best option for me was to get my existing block rebuilt. I had originally decided to go for a 2nd hand engine as these are generally a bit cheaper than a rebuild, however most had done around 30,000 miles, and what with my bottom end having broken at 41,000 miles, I couldn't see this being a sensible option in the long term. For a few hundred more my engine is now being rebuilt with new crank, bearings etc and will have the modified oil pump fitted to prevent that potentially causing engine failure in the future. I also get a full 12 month warranty, which as I will be using the car for work is a big peace of mind thing to me.
PM 22B-Andy from here as that's who is doing my rebuild.
Hope you get it sorted soon - you'll wince every time you walk past it until you do!
Cheers,
Brian