The Weber Alpha is a fine ECU if you have the correct map for your engine, to be honest any well mapped ECU will work. The problem with the Weber is you cannot map it yourself, as they lock it.
I would be surprised if your Weber has a wideband, I think you will find it is a narrow band sensor, which is completely different and cannot be used for adaptive mapping on an Emerald.
I really like the Emerald, as with a wideband I can get a pretty decent map using it's adaptive mapping function. Ideally the car should be set up on a Dyno and I plan to do this at some point, as with a decent (not me) mapper it can improve drive-ability hugely.
As to the wiring loom, I bought the Flying lead loom on ECU plug as a 60.00 GBP option, it can easily be adapted for any car.