New Engine Control Unit

Hi there, I am new to this site and would appreciate any advice with the following problem:
I have a 2005 A3 Sportback, 2.0 TFSI Quattro. The Emission Control light and the Engine Management light came on during the week and I am being told that I need to have a new Engine Control Unit fitted. The cost of this piece of kit in Dublin is around £450 (ex labor and VAT)
The A/C has also not been blowing cold for a while and I am being told that the gas is full but a new compressor is needed at a cost of €720 (ex labor and VAT).
Is it unusual for a the Engine Control Unit or the A/C Compressor to go in a car of this age?
Does anyone know what the cost of these items would be in the UK, as I could go up to Belfast to get the work done.
Any help would be greatly appreciated as I was shocked at the cost.
Regards,
Cunamara

Thanks Robin,
Got a diagnostic scan carried out on the car today. There was a notification that a software update was available, which, once completed, fixed the fault with the warning lights. There had been a recall on my car relating to this issue, so the diagnostic was carried out under warranty. Happy days!
Thanks for the suggestion.

Yep, huge relief! It was not an Audi recognised service centre; although they did claim to have the necessary diagnostic kit. Needless to say, I will not be going there again.