I don't think that many were re-engined in the day - think it was maybe 2 or 4 locos on a testing/evaluation basis (but I could be wrong).  I know First have recently re-engined 2 as well...

I still think that, for all their underpower at pulling away from stations, the HST is the best all-round train in use in Britain at the mo.  To improve on it, you'd need to electrify everywhere, which ain't going to happen here in Devon!