Hi I have just baught a 1998 omega 2.5 v6, nice car, but it has an annoying habit, it cuts out when i come to a stop or i am sitting idle for a little bit, anyone any ideas.

Clean out the breathers and the IACV. Look in the maintainance section for the guide on how to do this.

Sounds as if it maybe the 'crank sensor' on the way out, £55.00 from Vauxhall stealers, no great problem to fit, someone else will be along with there view.   ;)
best regards  

If it has little or no history of regular services put my money on oil breathers blocked...worth the effort replacing crank sensor as not too expensive and possibly will be on way out...does the eml light come on? if so flash up fault codes for definite solutions..best of luck with it

Can be crank sensor..

But if not,
possible areas fuel pump, cam sensor ( I have seen omegas with that causes also)

Don't just start changing items on spec, it can get quite expensive.
That's why garages do it.

Start at the beginning and check in a logical manner.

Start with doing a paperclip test iaw this link and post up your
codes.

http://www.omegaowners.com/forum/YaBB.pl?num=1189022687

Agree, do paperclip test.

If that shows nothing, idle issues are often caused by failing ICV (clean it), EGR (blank it) or air leaks (Fix it)