Hiya  welcome  do the pedal trick to see if there are any stored fault codes and post the results.
You will find a "how to"in the maintenance section.
Sounds as if a few oil changes and plugs might help.

Indeed. As said, pedal trick for you.

Count the flashes, post the codes, go from there.

What's the cam belt history/service schedule btw.

oklydokly update time thanks so far

The pedal trick

P0300 Random/multiple cylinder misfire detected
P0301 Cylinder 1 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0305 Cylinder 5 Misfire Detected
P0306 Cylinder 6 Misfire Detected
P0136 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0136 O2 sensor circuit slow response (Bank 1 Sensor 2)
P0136 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
P0136 O2 sensor circuit malfunction (Bank 1 Sensor 2)

cars been serviced every year by vauxhall tamworth up to 62k august 08 where i assume it changed owners

service history ends there although there is a sticker on the car from  IN n OUT saying next service due 25/12/10

mileage all seems to stack up against mots etc

rang vauxhall tamworth ref cam belt and was told they had not fitted one although the car has had a lot of new parts fitted exactly what they would not say but it was not down to any crash damage etc

so assume car has had no cambelt change at all opps and its been abused a bit by the sounds of things although the mileage of 74k seems genuine.

knocking nosie well its not a continuos knocking more like several big heavy knocks when you start and one when you turn off the engine noise also seems to be from the bottom of the engine ( sorry if i misled you live on main road so hard to hear at times)

will update profile etc I live on the Kent Coast Ramsgate

thanks so far been very helpful

Thanks Sandune I will check that out

just had the old boy from a couple of doors down round with a nother old boy who used to be a mechanic ( i think) anyway after a chat about the weather etc they had a listen to the car and thought it may be the mass fly wheel lots of hmmms and rrrrrs and shaking of heads ( i did not think an auto had one of those !!!!)

i will try and get a video on here
and have a look at ther points raise

thanks

paul

Thanks RobG

thats made my day was beging to think the repairs on this poor abused omega would cost more than the car

Thanks

Paul

Hmm does sound  like a knackered DMF on start-up but it's an auto. Starter motor disengaging with a bit of a clonk perhaps?

Engine sounds otherwise healthy to me but with the lack of service history I would give it a good service ASAP. Cam belt, coolant and oil change, oil, air and fuel filter, spark plugs, clean the breathers out, etc.

While you're at it have a look for anything loose that might be causing the noise.

Thanks everyone so far excellent advice all makes sense not that I am a mechanic havent messed about with cars for 25 years now and now theres all cables and hoses and thingys in there ooooooo  but got wifey to help me tomoorow so hoefully she will start the engine without running me over, crashing into the van or the house. will report back

Sandune spot on i think with water ingress at the time it was raining heavy and i had just got passed a wide load that was holding up traffic and everyone was accelerating away so lots of spray obviously dries out by the time i got to services so problem ressolved with fault codes

Darth great name engine does sound like its missing something after previously owning 2 x 2.6 and a 3.2 ( may need a starter motor)

Kevin thanks i had hoped someone would say starter motor could not locate the bloody thing but know where it is now and think your wright as it sound to the back and under to the side sort of

thanks guys appreciate your time and help will report back after tomorrow if wifey dont run me over