One of the reasons why alternators may melt down is the high speed they're turning at.
On a Rover 25, this wouldn't be the problem as these cars normally wouldn't run at high revs all the time, but a lot of Elise and Exige owners do appreciate to use the top of the rev band which can ultimately lead to the Alternator packing up.

This pulley kit increases the diameter of the OE pulley by nearly twice the size making it turn nearly half the revs it normally does..
This will help you saving the internal bearings etc.

You can't use this pulley together with a Bosch S2 Alternator!