I'm not sure whether this is a question or simply a humble warning to others.

Recently I bagan having trouble with my car's windscreen wipers not operating correctly. The wiper motor seemed to be working fine but the wipers would occasionally fail to park properly. Thinking that the wise option would be to exclude the cheapest possible failed item first I elected to change the wiper relay which might be at fault. Removing the relay I took it to a large national motor parts supplier (large black lettering on an orange background also selling bicycles) who had told me over the phone that they could supply a replacement. At the store they seemed less sure but with reference to the relay itself and to a well known manual-writers Vectra manual wiring diagram I left the store with a relay. At home I inserted the relay. Then my problems began.

The problem wasn't sorted and replacing the old relay only seemed to make matters worse. Now when I operated the wipers the engine stopped. No fuses blown or obvious clangers but now an undriveable car, at least in the rain. After several visits to various garages I have learned that the car's ECU (main) has been damaged and the bill will be several hundred pounds to repair. This was the most optimistic scenario as one "Car Electrical Specialist" said "I won't charge you as you've completely written of your car and I'm not sure I could fix it even if you asked me to!" That was a heart stopping moment!
This repair is ongoing and so the saga has not yet been written.

I'm not sure I want to play the blame game and point the finger at anyone here. Plainly I was the one who did the work. Trust me I feel like a royal tit having squandered a considerable chunk of my children's inheritance trying to save some "wonga". However what is facinating is the widespread and thorough lack of knowledge out there. Even many of those in the trade seem to have no idea about the significant vulnerabilities that modern car computer systems have to a simple "wrong relay" scenario. This is further exacerbated by the lack of standardisation that there is between the different manufacturers. Most diagnostic tools are manufacturer specific and even when employed by main dealers seem doomed to lead only to large (understatement) repair bills as they struggle to make sense of the "error codes" or the right course of action to find the underlying fault causing them.

Am I the only one who thinks that this situation is outragious? In this country I need a car and if I'm to have a newer efficient car then I must live "over the barrel" as any of these computer/ECU problems will mean an enormous bill or as one mechanic said " a written off" motor! It would seem that this situation is worsening as cars become ever more complicated and computerised. Even a simple brake pad change in some vehicles now requires it be plugged in to a computer. Is this really progress?

Som people have advised me that I may have a legal case against the parts supplier. Whatever happens in my case I'd like as many people as possible to know my mistake so that it need not be their own! I'll be the one in the pub with a long face, unless it's a rainy day!