I have recently had a problem with my Peugeot 106 1.1 Zest 2 (2001).
It began when I noticed the engine management light come on and that
the car was misfiring.

The AA looked at my vehicle and diagnosed the problem as a suspect
injector.

I took my car to the local dealership (not under warranty) and  they
charged me £80+VAT for a diagnosis which involved them diagnosing the
same problem as the AA guy had done for free!!

However when they fitted the injector they discovered that the wiring
loom had burnt out and that this also needed replacing bringing the
total to £215.

A day later when expecting a call to let me know when I could collect
my car I got a phone call telling me that they had unearthed a further
problem and that I needed a new ECU (they did not specify but I
presume this is the fuel one) and have quoted me £675 inclusive of
labour for the final part of the job bringing my repair bill to £890.

I am no expert on cars but this seems steep to me and wondered if
anyone could give me any advice/prices based on their own experiences
or knowledge?

Should the garage have identified the root of the problem sooner?

Many Thanks

James.