OK, news update. In trying to research prices I have found the following:
The 94-98 Omega TD requires an 096 battery which is 12v 72Ah and CCA 680. Oh yeah, and it's 278mm long (remember this, there'll be questions later)
The 99-> Omega TD has an 017 battery which is 12v 88Ah and CCA 750. This one is 354mm long.
My car is a 1998 model but has a battery that's 354mm long. This leads me to think that either (a) someone put the wrong one on by mistake, (b) someone put the bigger battery on thinking that the higher power would make the car start better or (c) the bigger battery was recommended when the towbar was fitted (would this be necessary....?)
I have always thought that the battery was 'kin huge but closer inspection shows that the battery is larger than the battery tray it should be sitting on.
The question now is this........... Does it actually make any difference which battery I put in it? Is the higher Ah rating any advantage or should I just stick to what the car should have in it? :-?
Thanks