Help - car has died.... ECU ??

Hi all,
Travelling along this morning and the oil level light popped on. So I stopped,topped up the oil but the light remained on. Definitely enough oil as read on the dipstick so thinking a faulty sensor I continued on my journey. About 20 miles later in traffic, just shunting at low speed and the car suddenly died. When attempting to restart it I had all the gears ( D,R,1,2,3,4 etc ) all lit up red. Engine management light and abs light also permanently on, it turns over but won't fire up. Just had fault codes read and the gearbox is saying missing command from ECU, Engine says missing command from ECU and any attempts to connect to the ECU directly fail ?? I've been told by a local garage that an ECU fault is plausible.
Does a faulty component on the ECU seem likely ?? After my alarm horn exploits I'm quite keen to try to repair it myself as I've heard there can be problems with drains blocking and water getting in there, does this all seem plausible to you knowledgable bods ??
Worst case scenario I understand I'm looking at the best part of 1K to get a new one and I've seen some A8 ECU's on A8parts - Does anyone know if these are different units or are they just generic ECU's flashed with a different program ??
any help/advice from you chaps is much appeciated as I'm feeling really deflated now and IF there is a good time for car problems it certainly isn't 2 bloody weeks before xmas
Help ....