don't understand why you didn't do this yourself.
it should be prettey straight forward job to grind the head of the bolt down - it needn't be ground fully off so no risk of grinding the tube - as long as it can be thin enough to deform when punching it through into the tube.
as for rattling inside, grind open the bottom bracket tube vent hole so it is large enough for the debris to drop through - the large hole would not weaken the frame at all.
How I wish I had. I did try drilling the bolts out initially but this didn't work as with limited tools I couldn't prevent the bolts spinning whilst drilling. After taking it to the bike shop, and for a fee that was, at the time less than the cost of buying a grinder, I thought why not, let the pros at it, especially as they were sympathetic to the fact I didn't want bits rattling around in the frame, and that the people they used were great at what they did.
I'm not repeating the thread. Again, but suffice to say what I was told would happen and what did were poles apart, and problems ensued.
Thankfully enigma did a great job of rectifying the abortion created by colourtech, so I'm happy, the build is complete and it's a lovely ride.
Knowing what I know now, I'd certainly tackle a job like this myself in future, or send it to enigma. If I wanted cavity wall insulation, I'd go to colourtech.