Stalling when dropping the clutch, when pulling up for instance, is often associates with dodgy wiring to the map sensor. Because of tightness in the loom, engine rock eventually breaks the wires down. Personally I've never heard of an MPi ECU 'going wrong' through general wear and tear and I've also never heard of a replacement for £120. Don't forget that the ECU is synced to the immobiliser/alarm so to replace it you'll also have to replace the alarm module and your key fobs. And a second hand set usually goes for around 200 on ebay.
You might want to consider a replacement engine bay loom before a replacement ECU. The wiring is more likely to fail than the ECU.
Edited by minicooper1.3i, 28 July 2010 - 01:03 PM.